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Change project structure to a Maven Java project + Refactor (#2816)

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Aitor Fidalgo Sánchez
2021-11-12 07:59:36 +01:00
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commit 9fb3364ccc
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package com.thealgorithms.ciphers;
import java.math.BigInteger;
import java.util.Scanner;
/**
* This class is build to demonstrate the application of the AES-algorithm on a
* single 128-Bit block of data.
*/
public class AES {
/**
* Precalculated values for x to the power of 2 in Rijndaels galois field.
* Used as 'RCON' during the key expansion.
*/
private static final int[] RCON = {
0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39,
0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a,
0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8,
0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef,
0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc,
0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b,
0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3,
0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94,
0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20,
0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35,
0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f,
0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04,
0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63,
0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd,
0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d
};
/**
* Rijndael S-box Substitution table used for encryption in the subBytes
* step, as well as the key expansion.
*/
private static final int[] SBOX = {
0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F, 0xC5, 0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76,
0xCA, 0x82, 0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0, 0xAD, 0xD4, 0xA2, 0xAF, 0x9C, 0xA4, 0x72, 0xC0,
0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC, 0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15,
0x04, 0xC7, 0x23, 0xC3, 0x18, 0x96, 0x05, 0x9A, 0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27, 0xB2, 0x75,
0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0, 0x52, 0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84,
0x53, 0xD1, 0x00, 0xED, 0x20, 0xFC, 0xB1, 0x5B, 0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58, 0xCF,
0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85, 0x45, 0xF9, 0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8,
0x51, 0xA3, 0x40, 0x8F, 0x92, 0x9D, 0x38, 0xF5, 0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2,
0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17, 0xC4, 0xA7, 0x7E, 0x3D, 0x64, 0x5D, 0x19, 0x73,
0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A, 0x90, 0x88, 0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB,
0xE0, 0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C, 0xC2, 0xD3, 0xAC, 0x62, 0x91, 0x95, 0xE4, 0x79,
0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E, 0xA9, 0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08,
0xBA, 0x78, 0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6, 0xE8, 0xDD, 0x74, 0x1F, 0x4B, 0xBD, 0x8B, 0x8A,
0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E, 0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E,
0xE1, 0xF8, 0x98, 0x11, 0x69, 0xD9, 0x8E, 0x94, 0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55, 0x28, 0xDF,
0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68, 0x41, 0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16
};
/**
* Inverse Rijndael S-box Substitution table used for decryption in the
* subBytesDec step.
*/
private static final int[] INVERSE_SBOX = {
0x52, 0x09, 0x6A, 0xD5, 0x30, 0x36, 0xA5, 0x38, 0xBF, 0x40, 0xA3, 0x9E, 0x81, 0xF3, 0xD7, 0xFB,
0x7C, 0xE3, 0x39, 0x82, 0x9B, 0x2F, 0xFF, 0x87, 0x34, 0x8E, 0x43, 0x44, 0xC4, 0xDE, 0xE9, 0xCB,
0x54, 0x7B, 0x94, 0x32, 0xA6, 0xC2, 0x23, 0x3D, 0xEE, 0x4C, 0x95, 0x0B, 0x42, 0xFA, 0xC3, 0x4E,
0x08, 0x2E, 0xA1, 0x66, 0x28, 0xD9, 0x24, 0xB2, 0x76, 0x5B, 0xA2, 0x49, 0x6D, 0x8B, 0xD1, 0x25,
0x72, 0xF8, 0xF6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xD4, 0xA4, 0x5C, 0xCC, 0x5D, 0x65, 0xB6, 0x92,
0x6C, 0x70, 0x48, 0x50, 0xFD, 0xED, 0xB9, 0xDA, 0x5E, 0x15, 0x46, 0x57, 0xA7, 0x8D, 0x9D, 0x84,
0x90, 0xD8, 0xAB, 0x00, 0x8C, 0xBC, 0xD3, 0x0A, 0xF7, 0xE4, 0x58, 0x05, 0xB8, 0xB3, 0x45, 0x06,
0xD0, 0x2C, 0x1E, 0x8F, 0xCA, 0x3F, 0x0F, 0x02, 0xC1, 0xAF, 0xBD, 0x03, 0x01, 0x13, 0x8A, 0x6B,
0x3A, 0x91, 0x11, 0x41, 0x4F, 0x67, 0xDC, 0xEA, 0x97, 0xF2, 0xCF, 0xCE, 0xF0, 0xB4, 0xE6, 0x73,
0x96, 0xAC, 0x74, 0x22, 0xE7, 0xAD, 0x35, 0x85, 0xE2, 0xF9, 0x37, 0xE8, 0x1C, 0x75, 0xDF, 0x6E,
0x47, 0xF1, 0x1A, 0x71, 0x1D, 0x29, 0xC5, 0x89, 0x6F, 0xB7, 0x62, 0x0E, 0xAA, 0x18, 0xBE, 0x1B,
0xFC, 0x56, 0x3E, 0x4B, 0xC6, 0xD2, 0x79, 0x20, 0x9A, 0xDB, 0xC0, 0xFE, 0x78, 0xCD, 0x5A, 0xF4,
0x1F, 0xDD, 0xA8, 0x33, 0x88, 0x07, 0xC7, 0x31, 0xB1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xEC, 0x5F,
0x60, 0x51, 0x7F, 0xA9, 0x19, 0xB5, 0x4A, 0x0D, 0x2D, 0xE5, 0x7A, 0x9F, 0x93, 0xC9, 0x9C, 0xEF,
0xA0, 0xE0, 0x3B, 0x4D, 0xAE, 0x2A, 0xF5, 0xB0, 0xC8, 0xEB, 0xBB, 0x3C, 0x83, 0x53, 0x99, 0x61,
0x17, 0x2B, 0x04, 0x7E, 0xBA, 0x77, 0xD6, 0x26, 0xE1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0C, 0x7D
};
/**
* Precalculated lookup table for galois field multiplication by 2 used in
* the MixColums step during encryption.
*/
private static final int[] MULT2 = {
0x00, 0x02, 0x04, 0x06, 0x08, 0x0a, 0x0c, 0x0e, 0x10, 0x12, 0x14, 0x16, 0x18, 0x1a, 0x1c, 0x1e,
0x20, 0x22, 0x24, 0x26, 0x28, 0x2a, 0x2c, 0x2e, 0x30, 0x32, 0x34, 0x36, 0x38, 0x3a, 0x3c, 0x3e,
0x40, 0x42, 0x44, 0x46, 0x48, 0x4a, 0x4c, 0x4e, 0x50, 0x52, 0x54, 0x56, 0x58, 0x5a, 0x5c, 0x5e,
0x60, 0x62, 0x64, 0x66, 0x68, 0x6a, 0x6c, 0x6e, 0x70, 0x72, 0x74, 0x76, 0x78, 0x7a, 0x7c, 0x7e,
0x80, 0x82, 0x84, 0x86, 0x88, 0x8a, 0x8c, 0x8e, 0x90, 0x92, 0x94, 0x96, 0x98, 0x9a, 0x9c, 0x9e,
0xa0, 0xa2, 0xa4, 0xa6, 0xa8, 0xaa, 0xac, 0xae, 0xb0, 0xb2, 0xb4, 0xb6, 0xb8, 0xba, 0xbc, 0xbe,
0xc0, 0xc2, 0xc4, 0xc6, 0xc8, 0xca, 0xcc, 0xce, 0xd0, 0xd2, 0xd4, 0xd6, 0xd8, 0xda, 0xdc, 0xde,
0xe0, 0xe2, 0xe4, 0xe6, 0xe8, 0xea, 0xec, 0xee, 0xf0, 0xf2, 0xf4, 0xf6, 0xf8, 0xfa, 0xfc, 0xfe,
0x1b, 0x19, 0x1f, 0x1d, 0x13, 0x11, 0x17, 0x15, 0x0b, 0x09, 0x0f, 0x0d, 0x03, 0x01, 0x07, 0x05,
0x3b, 0x39, 0x3f, 0x3d, 0x33, 0x31, 0x37, 0x35, 0x2b, 0x29, 0x2f, 0x2d, 0x23, 0x21, 0x27, 0x25,
0x5b, 0x59, 0x5f, 0x5d, 0x53, 0x51, 0x57, 0x55, 0x4b, 0x49, 0x4f, 0x4d, 0x43, 0x41, 0x47, 0x45,
0x7b, 0x79, 0x7f, 0x7d, 0x73, 0x71, 0x77, 0x75, 0x6b, 0x69, 0x6f, 0x6d, 0x63, 0x61, 0x67, 0x65,
0x9b, 0x99, 0x9f, 0x9d, 0x93, 0x91, 0x97, 0x95, 0x8b, 0x89, 0x8f, 0x8d, 0x83, 0x81, 0x87, 0x85,
0xbb, 0xb9, 0xbf, 0xbd, 0xb3, 0xb1, 0xb7, 0xb5, 0xab, 0xa9, 0xaf, 0xad, 0xa3, 0xa1, 0xa7, 0xa5,
0xdb, 0xd9, 0xdf, 0xdd, 0xd3, 0xd1, 0xd7, 0xd5, 0xcb, 0xc9, 0xcf, 0xcd, 0xc3, 0xc1, 0xc7, 0xc5,
0xfb, 0xf9, 0xff, 0xfd, 0xf3, 0xf1, 0xf7, 0xf5, 0xeb, 0xe9, 0xef, 0xed, 0xe3, 0xe1, 0xe7, 0xe5
};
/**
* Precalculated lookup table for galois field multiplication by 3 used in
* the MixColums step during encryption.
*/
private static final int[] MULT3 = {
0x00, 0x03, 0x06, 0x05, 0x0c, 0x0f, 0x0a, 0x09, 0x18, 0x1b, 0x1e, 0x1d, 0x14, 0x17, 0x12, 0x11,
0x30, 0x33, 0x36, 0x35, 0x3c, 0x3f, 0x3a, 0x39, 0x28, 0x2b, 0x2e, 0x2d, 0x24, 0x27, 0x22, 0x21,
0x60, 0x63, 0x66, 0x65, 0x6c, 0x6f, 0x6a, 0x69, 0x78, 0x7b, 0x7e, 0x7d, 0x74, 0x77, 0x72, 0x71,
0x50, 0x53, 0x56, 0x55, 0x5c, 0x5f, 0x5a, 0x59, 0x48, 0x4b, 0x4e, 0x4d, 0x44, 0x47, 0x42, 0x41,
0xc0, 0xc3, 0xc6, 0xc5, 0xcc, 0xcf, 0xca, 0xc9, 0xd8, 0xdb, 0xde, 0xdd, 0xd4, 0xd7, 0xd2, 0xd1,
0xf0, 0xf3, 0xf6, 0xf5, 0xfc, 0xff, 0xfa, 0xf9, 0xe8, 0xeb, 0xee, 0xed, 0xe4, 0xe7, 0xe2, 0xe1,
0xa0, 0xa3, 0xa6, 0xa5, 0xac, 0xaf, 0xaa, 0xa9, 0xb8, 0xbb, 0xbe, 0xbd, 0xb4, 0xb7, 0xb2, 0xb1,
0x90, 0x93, 0x96, 0x95, 0x9c, 0x9f, 0x9a, 0x99, 0x88, 0x8b, 0x8e, 0x8d, 0x84, 0x87, 0x82, 0x81,
0x9b, 0x98, 0x9d, 0x9e, 0x97, 0x94, 0x91, 0x92, 0x83, 0x80, 0x85, 0x86, 0x8f, 0x8c, 0x89, 0x8a,
0xab, 0xa8, 0xad, 0xae, 0xa7, 0xa4, 0xa1, 0xa2, 0xb3, 0xb0, 0xb5, 0xb6, 0xbf, 0xbc, 0xb9, 0xba,
0xfb, 0xf8, 0xfd, 0xfe, 0xf7, 0xf4, 0xf1, 0xf2, 0xe3, 0xe0, 0xe5, 0xe6, 0xef, 0xec, 0xe9, 0xea,
0xcb, 0xc8, 0xcd, 0xce, 0xc7, 0xc4, 0xc1, 0xc2, 0xd3, 0xd0, 0xd5, 0xd6, 0xdf, 0xdc, 0xd9, 0xda,
0x5b, 0x58, 0x5d, 0x5e, 0x57, 0x54, 0x51, 0x52, 0x43, 0x40, 0x45, 0x46, 0x4f, 0x4c, 0x49, 0x4a,
0x6b, 0x68, 0x6d, 0x6e, 0x67, 0x64, 0x61, 0x62, 0x73, 0x70, 0x75, 0x76, 0x7f, 0x7c, 0x79, 0x7a,
0x3b, 0x38, 0x3d, 0x3e, 0x37, 0x34, 0x31, 0x32, 0x23, 0x20, 0x25, 0x26, 0x2f, 0x2c, 0x29, 0x2a,
0x0b, 0x08, 0x0d, 0x0e, 0x07, 0x04, 0x01, 0x02, 0x13, 0x10, 0x15, 0x16, 0x1f, 0x1c, 0x19, 0x1a
};
/**
* Precalculated lookup table for galois field multiplication by 9 used in
* the MixColums step during decryption.
*/
private static final int[] MULT9 = {
0x00, 0x09, 0x12, 0x1b, 0x24, 0x2d, 0x36, 0x3f, 0x48, 0x41, 0x5a, 0x53, 0x6c, 0x65, 0x7e, 0x77,
0x90, 0x99, 0x82, 0x8b, 0xb4, 0xbd, 0xa6, 0xaf, 0xd8, 0xd1, 0xca, 0xc3, 0xfc, 0xf5, 0xee, 0xe7,
0x3b, 0x32, 0x29, 0x20, 0x1f, 0x16, 0x0d, 0x04, 0x73, 0x7a, 0x61, 0x68, 0x57, 0x5e, 0x45, 0x4c,
0xab, 0xa2, 0xb9, 0xb0, 0x8f, 0x86, 0x9d, 0x94, 0xe3, 0xea, 0xf1, 0xf8, 0xc7, 0xce, 0xd5, 0xdc,
0x76, 0x7f, 0x64, 0x6d, 0x52, 0x5b, 0x40, 0x49, 0x3e, 0x37, 0x2c, 0x25, 0x1a, 0x13, 0x08, 0x01,
0xe6, 0xef, 0xf4, 0xfd, 0xc2, 0xcb, 0xd0, 0xd9, 0xae, 0xa7, 0xbc, 0xb5, 0x8a, 0x83, 0x98, 0x91,
0x4d, 0x44, 0x5f, 0x56, 0x69, 0x60, 0x7b, 0x72, 0x05, 0x0c, 0x17, 0x1e, 0x21, 0x28, 0x33, 0x3a,
0xdd, 0xd4, 0xcf, 0xc6, 0xf9, 0xf0, 0xeb, 0xe2, 0x95, 0x9c, 0x87, 0x8e, 0xb1, 0xb8, 0xa3, 0xaa,
0xec, 0xe5, 0xfe, 0xf7, 0xc8, 0xc1, 0xda, 0xd3, 0xa4, 0xad, 0xb6, 0xbf, 0x80, 0x89, 0x92, 0x9b,
0x7c, 0x75, 0x6e, 0x67, 0x58, 0x51, 0x4a, 0x43, 0x34, 0x3d, 0x26, 0x2f, 0x10, 0x19, 0x02, 0x0b,
0xd7, 0xde, 0xc5, 0xcc, 0xf3, 0xfa, 0xe1, 0xe8, 0x9f, 0x96, 0x8d, 0x84, 0xbb, 0xb2, 0xa9, 0xa0,
0x47, 0x4e, 0x55, 0x5c, 0x63, 0x6a, 0x71, 0x78, 0x0f, 0x06, 0x1d, 0x14, 0x2b, 0x22, 0x39, 0x30,
0x9a, 0x93, 0x88, 0x81, 0xbe, 0xb7, 0xac, 0xa5, 0xd2, 0xdb, 0xc0, 0xc9, 0xf6, 0xff, 0xe4, 0xed,
0x0a, 0x03, 0x18, 0x11, 0x2e, 0x27, 0x3c, 0x35, 0x42, 0x4b, 0x50, 0x59, 0x66, 0x6f, 0x74, 0x7d,
0xa1, 0xa8, 0xb3, 0xba, 0x85, 0x8c, 0x97, 0x9e, 0xe9, 0xe0, 0xfb, 0xf2, 0xcd, 0xc4, 0xdf, 0xd6,
0x31, 0x38, 0x23, 0x2a, 0x15, 0x1c, 0x07, 0x0e, 0x79, 0x70, 0x6b, 0x62, 0x5d, 0x54, 0x4f, 0x46
};
/**
* Precalculated lookup table for galois field multiplication by 11 used in
* the MixColums step during decryption.
*/
private static final int[] MULT11 = {
0x00, 0x0b, 0x16, 0x1d, 0x2c, 0x27, 0x3a, 0x31, 0x58, 0x53, 0x4e, 0x45, 0x74, 0x7f, 0x62, 0x69,
0xb0, 0xbb, 0xa6, 0xad, 0x9c, 0x97, 0x8a, 0x81, 0xe8, 0xe3, 0xfe, 0xf5, 0xc4, 0xcf, 0xd2, 0xd9,
0x7b, 0x70, 0x6d, 0x66, 0x57, 0x5c, 0x41, 0x4a, 0x23, 0x28, 0x35, 0x3e, 0x0f, 0x04, 0x19, 0x12,
0xcb, 0xc0, 0xdd, 0xd6, 0xe7, 0xec, 0xf1, 0xfa, 0x93, 0x98, 0x85, 0x8e, 0xbf, 0xb4, 0xa9, 0xa2,
0xf6, 0xfd, 0xe0, 0xeb, 0xda, 0xd1, 0xcc, 0xc7, 0xae, 0xa5, 0xb8, 0xb3, 0x82, 0x89, 0x94, 0x9f,
0x46, 0x4d, 0x50, 0x5b, 0x6a, 0x61, 0x7c, 0x77, 0x1e, 0x15, 0x08, 0x03, 0x32, 0x39, 0x24, 0x2f,
0x8d, 0x86, 0x9b, 0x90, 0xa1, 0xaa, 0xb7, 0xbc, 0xd5, 0xde, 0xc3, 0xc8, 0xf9, 0xf2, 0xef, 0xe4,
0x3d, 0x36, 0x2b, 0x20, 0x11, 0x1a, 0x07, 0x0c, 0x65, 0x6e, 0x73, 0x78, 0x49, 0x42, 0x5f, 0x54,
0xf7, 0xfc, 0xe1, 0xea, 0xdb, 0xd0, 0xcd, 0xc6, 0xaf, 0xa4, 0xb9, 0xb2, 0x83, 0x88, 0x95, 0x9e,
0x47, 0x4c, 0x51, 0x5a, 0x6b, 0x60, 0x7d, 0x76, 0x1f, 0x14, 0x09, 0x02, 0x33, 0x38, 0x25, 0x2e,
0x8c, 0x87, 0x9a, 0x91, 0xa0, 0xab, 0xb6, 0xbd, 0xd4, 0xdf, 0xc2, 0xc9, 0xf8, 0xf3, 0xee, 0xe5,
0x3c, 0x37, 0x2a, 0x21, 0x10, 0x1b, 0x06, 0x0d, 0x64, 0x6f, 0x72, 0x79, 0x48, 0x43, 0x5e, 0x55,
0x01, 0x0a, 0x17, 0x1c, 0x2d, 0x26, 0x3b, 0x30, 0x59, 0x52, 0x4f, 0x44, 0x75, 0x7e, 0x63, 0x68,
0xb1, 0xba, 0xa7, 0xac, 0x9d, 0x96, 0x8b, 0x80, 0xe9, 0xe2, 0xff, 0xf4, 0xc5, 0xce, 0xd3, 0xd8,
0x7a, 0x71, 0x6c, 0x67, 0x56, 0x5d, 0x40, 0x4b, 0x22, 0x29, 0x34, 0x3f, 0x0e, 0x05, 0x18, 0x13,
0xca, 0xc1, 0xdc, 0xd7, 0xe6, 0xed, 0xf0, 0xfb, 0x92, 0x99, 0x84, 0x8f, 0xbe, 0xb5, 0xa8, 0xa3
};
/**
* Precalculated lookup table for galois field multiplication by 13 used in
* the MixColums step during decryption.
*/
private static final int[] MULT13 = {
0x00, 0x0d, 0x1a, 0x17, 0x34, 0x39, 0x2e, 0x23, 0x68, 0x65, 0x72, 0x7f, 0x5c, 0x51, 0x46, 0x4b,
0xd0, 0xdd, 0xca, 0xc7, 0xe4, 0xe9, 0xfe, 0xf3, 0xb8, 0xb5, 0xa2, 0xaf, 0x8c, 0x81, 0x96, 0x9b,
0xbb, 0xb6, 0xa1, 0xac, 0x8f, 0x82, 0x95, 0x98, 0xd3, 0xde, 0xc9, 0xc4, 0xe7, 0xea, 0xfd, 0xf0,
0x6b, 0x66, 0x71, 0x7c, 0x5f, 0x52, 0x45, 0x48, 0x03, 0x0e, 0x19, 0x14, 0x37, 0x3a, 0x2d, 0x20,
0x6d, 0x60, 0x77, 0x7a, 0x59, 0x54, 0x43, 0x4e, 0x05, 0x08, 0x1f, 0x12, 0x31, 0x3c, 0x2b, 0x26,
0xbd, 0xb0, 0xa7, 0xaa, 0x89, 0x84, 0x93, 0x9e, 0xd5, 0xd8, 0xcf, 0xc2, 0xe1, 0xec, 0xfb, 0xf6,
0xd6, 0xdb, 0xcc, 0xc1, 0xe2, 0xef, 0xf8, 0xf5, 0xbe, 0xb3, 0xa4, 0xa9, 0x8a, 0x87, 0x90, 0x9d,
0x06, 0x0b, 0x1c, 0x11, 0x32, 0x3f, 0x28, 0x25, 0x6e, 0x63, 0x74, 0x79, 0x5a, 0x57, 0x40, 0x4d,
0xda, 0xd7, 0xc0, 0xcd, 0xee, 0xe3, 0xf4, 0xf9, 0xb2, 0xbf, 0xa8, 0xa5, 0x86, 0x8b, 0x9c, 0x91,
0x0a, 0x07, 0x10, 0x1d, 0x3e, 0x33, 0x24, 0x29, 0x62, 0x6f, 0x78, 0x75, 0x56, 0x5b, 0x4c, 0x41,
0x61, 0x6c, 0x7b, 0x76, 0x55, 0x58, 0x4f, 0x42, 0x09, 0x04, 0x13, 0x1e, 0x3d, 0x30, 0x27, 0x2a,
0xb1, 0xbc, 0xab, 0xa6, 0x85, 0x88, 0x9f, 0x92, 0xd9, 0xd4, 0xc3, 0xce, 0xed, 0xe0, 0xf7, 0xfa,
0xb7, 0xba, 0xad, 0xa0, 0x83, 0x8e, 0x99, 0x94, 0xdf, 0xd2, 0xc5, 0xc8, 0xeb, 0xe6, 0xf1, 0xfc,
0x67, 0x6a, 0x7d, 0x70, 0x53, 0x5e, 0x49, 0x44, 0x0f, 0x02, 0x15, 0x18, 0x3b, 0x36, 0x21, 0x2c,
0x0c, 0x01, 0x16, 0x1b, 0x38, 0x35, 0x22, 0x2f, 0x64, 0x69, 0x7e, 0x73, 0x50, 0x5d, 0x4a, 0x47,
0xdc, 0xd1, 0xc6, 0xcb, 0xe8, 0xe5, 0xf2, 0xff, 0xb4, 0xb9, 0xae, 0xa3, 0x80, 0x8d, 0x9a, 0x97
};
/**
* Precalculated lookup table for galois field multiplication by 14 used in
* the MixColums step during decryption.
*/
private static final int[] MULT14 = {
0x00, 0x0e, 0x1c, 0x12, 0x38, 0x36, 0x24, 0x2a, 0x70, 0x7e, 0x6c, 0x62, 0x48, 0x46, 0x54, 0x5a,
0xe0, 0xee, 0xfc, 0xf2, 0xd8, 0xd6, 0xc4, 0xca, 0x90, 0x9e, 0x8c, 0x82, 0xa8, 0xa6, 0xb4, 0xba,
0xdb, 0xd5, 0xc7, 0xc9, 0xe3, 0xed, 0xff, 0xf1, 0xab, 0xa5, 0xb7, 0xb9, 0x93, 0x9d, 0x8f, 0x81,
0x3b, 0x35, 0x27, 0x29, 0x03, 0x0d, 0x1f, 0x11, 0x4b, 0x45, 0x57, 0x59, 0x73, 0x7d, 0x6f, 0x61,
0xad, 0xa3, 0xb1, 0xbf, 0x95, 0x9b, 0x89, 0x87, 0xdd, 0xd3, 0xc1, 0xcf, 0xe5, 0xeb, 0xf9, 0xf7,
0x4d, 0x43, 0x51, 0x5f, 0x75, 0x7b, 0x69, 0x67, 0x3d, 0x33, 0x21, 0x2f, 0x05, 0x0b, 0x19, 0x17,
0x76, 0x78, 0x6a, 0x64, 0x4e, 0x40, 0x52, 0x5c, 0x06, 0x08, 0x1a, 0x14, 0x3e, 0x30, 0x22, 0x2c,
0x96, 0x98, 0x8a, 0x84, 0xae, 0xa0, 0xb2, 0xbc, 0xe6, 0xe8, 0xfa, 0xf4, 0xde, 0xd0, 0xc2, 0xcc,
0x41, 0x4f, 0x5d, 0x53, 0x79, 0x77, 0x65, 0x6b, 0x31, 0x3f, 0x2d, 0x23, 0x09, 0x07, 0x15, 0x1b,
0xa1, 0xaf, 0xbd, 0xb3, 0x99, 0x97, 0x85, 0x8b, 0xd1, 0xdf, 0xcd, 0xc3, 0xe9, 0xe7, 0xf5, 0xfb,
0x9a, 0x94, 0x86, 0x88, 0xa2, 0xac, 0xbe, 0xb0, 0xea, 0xe4, 0xf6, 0xf8, 0xd2, 0xdc, 0xce, 0xc0,
0x7a, 0x74, 0x66, 0x68, 0x42, 0x4c, 0x5e, 0x50, 0x0a, 0x04, 0x16, 0x18, 0x32, 0x3c, 0x2e, 0x20,
0xec, 0xe2, 0xf0, 0xfe, 0xd4, 0xda, 0xc8, 0xc6, 0x9c, 0x92, 0x80, 0x8e, 0xa4, 0xaa, 0xb8, 0xb6,
0x0c, 0x02, 0x10, 0x1e, 0x34, 0x3a, 0x28, 0x26, 0x7c, 0x72, 0x60, 0x6e, 0x44, 0x4a, 0x58, 0x56,
0x37, 0x39, 0x2b, 0x25, 0x0f, 0x01, 0x13, 0x1d, 0x47, 0x49, 0x5b, 0x55, 0x7f, 0x71, 0x63, 0x6d,
0xd7, 0xd9, 0xcb, 0xc5, 0xef, 0xe1, 0xf3, 0xfd, 0xa7, 0xa9, 0xbb, 0xb5, 0x9f, 0x91, 0x83, 0x8d
};
/**
* Subroutine of the Rijndael key expansion.
*/
public static BigInteger scheduleCore(BigInteger t, int rconCounter) {
StringBuilder rBytes = new StringBuilder(t.toString(16));
// Add zero padding
while (rBytes.length() < 8) {
rBytes.insert(0, "0");
}
// rotate the first 16 bits to the back
String rotatingBytes = rBytes.substring(0, 2);
String fixedBytes = rBytes.substring(2);
rBytes = new StringBuilder(fixedBytes + rotatingBytes);
// apply S-Box to all 8-Bit Substrings
for (int i = 0; i < 4; i++) {
StringBuilder currentByteBits = new StringBuilder(rBytes.substring(i * 2, (i + 1) * 2));
int currentByte = Integer.parseInt(currentByteBits.toString(), 16);
currentByte = SBOX[currentByte];
// add the current RCON value to the first byte
if (i == 0) {
currentByte = currentByte ^ RCON[rconCounter];
}
currentByteBits = new StringBuilder(Integer.toHexString(currentByte));
// Add zero padding
while (currentByteBits.length() < 2) {
currentByteBits.insert(0, '0');
}
// replace bytes in original string
rBytes = new StringBuilder(rBytes.substring(0, i * 2) + currentByteBits + rBytes.substring((i + 1) * 2));
}
// t = new BigInteger(rBytes, 16);
// return t;
return new BigInteger(rBytes.toString(), 16);
}
/**
* Returns an array of 10 + 1 round keys that are calculated by using
* Rijndael key schedule
*
* @return array of 10 + 1 round keys
*/
public static BigInteger[] keyExpansion(BigInteger initialKey) {
BigInteger[] roundKeys = {
initialKey,
new BigInteger("0"),
new BigInteger("0"),
new BigInteger("0"),
new BigInteger("0"),
new BigInteger("0"),
new BigInteger("0"),
new BigInteger("0"),
new BigInteger("0"),
new BigInteger("0"),
new BigInteger("0"),};
// initialize rcon iteration
int rconCounter = 1;
for (int i = 1; i < 11; i++) {
// get the previous 32 bits the key
BigInteger t = roundKeys[i - 1].remainder(new BigInteger("100000000", 16));
// split previous key into 8-bit segments
BigInteger[] prevKey = {
roundKeys[i - 1].remainder(new BigInteger("100000000", 16)),
roundKeys[i - 1]
.remainder(new BigInteger("10000000000000000", 16))
.divide(new BigInteger("100000000", 16)),
roundKeys[i - 1]
.remainder(new BigInteger("1000000000000000000000000", 16))
.divide(new BigInteger("10000000000000000", 16)),
roundKeys[i - 1].divide(new BigInteger("1000000000000000000000000", 16)),};
// run schedule core
t = scheduleCore(t, rconCounter);
rconCounter += 1;
// Calculate partial round key
BigInteger t0 = t.xor(prevKey[3]);
BigInteger t1 = t0.xor(prevKey[2]);
BigInteger t2 = t1.xor(prevKey[1]);
BigInteger t3 = t2.xor(prevKey[0]);
// Join round key segments
t2 = t2.multiply(new BigInteger("100000000", 16));
t1 = t1.multiply(new BigInteger("10000000000000000", 16));
t0 = t0.multiply(new BigInteger("1000000000000000000000000", 16));
roundKeys[i] = t0.add(t1).add(t2).add(t3);
}
return roundKeys;
}
/**
* representation of the input 128-bit block as an array of 8-bit integers.
*
* @param block of 128-bit integers
* @return array of 8-bit integers
*/
public static int[] splitBlockIntoCells(BigInteger block) {
int[] cells = new int[16];
StringBuilder blockBits = new StringBuilder(block.toString(2));
// Append leading 0 for full "128-bit" string
while (blockBits.length() < 128) {
blockBits.insert(0, '0');
}
// split 128 to 8 bit cells
for (int i = 0; i < cells.length; i++) {
String cellBits = blockBits.substring(8 * i, 8 * (i + 1));
cells[i] = Integer.parseInt(cellBits, 2);
}
return cells;
}
/**
* Returns the 128-bit BigInteger representation of the input of an array of
* 8-bit integers.
*
* @param cells that we need to merge
* @return block of merged cells
*/
public static BigInteger mergeCellsIntoBlock(int[] cells) {
StringBuilder blockBits = new StringBuilder();
for (int i = 0; i < 16; i++) {
StringBuilder cellBits = new StringBuilder(Integer.toBinaryString(cells[i]));
// Append leading 0 for full "8-bit" strings
while (cellBits.length() < 8) {
cellBits.insert(0, '0');
}
blockBits.append(cellBits);
}
return new BigInteger(blockBits.toString(), 2);
}
/**
* @return ciphertext XOR key
*/
public static BigInteger addRoundKey(BigInteger ciphertext, BigInteger key) {
return ciphertext.xor(key);
}
/**
* substitutes 8-Bit long substrings of the input using the S-Box and
* returns the result.
*
* @return subtraction Output
*/
public static BigInteger subBytes(BigInteger ciphertext) {
int[] cells = splitBlockIntoCells(ciphertext);
for (int i = 0; i < 16; i++) {
cells[i] = SBOX[cells[i]];
}
return mergeCellsIntoBlock(cells);
}
/**
* substitutes 8-Bit long substrings of the input using the inverse S-Box
* for decryption and returns the result.
*
* @return subtraction Output
*/
public static BigInteger subBytesDec(BigInteger ciphertext) {
int[] cells = splitBlockIntoCells(ciphertext);
for (int i = 0; i < 16; i++) {
cells[i] = INVERSE_SBOX[cells[i]];
}
return mergeCellsIntoBlock(cells);
}
/**
* Cell permutation step. Shifts cells within the rows of the input and
* returns the result.
*/
public static BigInteger shiftRows(BigInteger ciphertext) {
int[] cells = splitBlockIntoCells(ciphertext);
int[] output = new int[16];
// do nothing in the first row
output[0] = cells[0];
output[4] = cells[4];
output[8] = cells[8];
output[12] = cells[12];
// shift the second row backwards by one cell
output[1] = cells[5];
output[5] = cells[9];
output[9] = cells[13];
output[13] = cells[1];
// shift the third row backwards by two cell
output[2] = cells[10];
output[6] = cells[14];
output[10] = cells[2];
output[14] = cells[6];
// shift the forth row backwards by tree cell
output[3] = cells[15];
output[7] = cells[3];
output[11] = cells[7];
output[15] = cells[11];
return mergeCellsIntoBlock(output);
}
/**
* Cell permutation step for decryption . Shifts cells within the rows of
* the input and returns the result.
*/
public static BigInteger shiftRowsDec(BigInteger ciphertext) {
int[] cells = splitBlockIntoCells(ciphertext);
int[] output = new int[16];
// do nothing in the first row
output[0] = cells[0];
output[4] = cells[4];
output[8] = cells[8];
output[12] = cells[12];
// shift the second row forwards by one cell
output[1] = cells[13];
output[5] = cells[1];
output[9] = cells[5];
output[13] = cells[9];
// shift the third row forwards by two cell
output[2] = cells[10];
output[6] = cells[14];
output[10] = cells[2];
output[14] = cells[6];
// shift the forth row forwards by tree cell
output[3] = cells[7];
output[7] = cells[11];
output[11] = cells[15];
output[15] = cells[3];
return mergeCellsIntoBlock(output);
}
/**
* Applies the Rijndael MixColumns to the input and returns the result.
*/
public static BigInteger mixColumns(BigInteger ciphertext) {
int[] cells = splitBlockIntoCells(ciphertext);
int[] outputCells = new int[16];
for (int i = 0; i < 4; i++) {
int[] row = {cells[i * 4], cells[i * 4 + 1], cells[i * 4 + 2], cells[i * 4 + 3]};
outputCells[i * 4] = MULT2[row[0]] ^ MULT3[row[1]] ^ row[2] ^ row[3];
outputCells[i * 4 + 1] = row[0] ^ MULT2[row[1]] ^ MULT3[row[2]] ^ row[3];
outputCells[i * 4 + 2] = row[0] ^ row[1] ^ MULT2[row[2]] ^ MULT3[row[3]];
outputCells[i * 4 + 3] = MULT3[row[0]] ^ row[1] ^ row[2] ^ MULT2[row[3]];
}
return mergeCellsIntoBlock(outputCells);
}
/**
* Applies the inverse Rijndael MixColumns for decryption to the input and
* returns the result.
*/
public static BigInteger mixColumnsDec(BigInteger ciphertext) {
int[] cells = splitBlockIntoCells(ciphertext);
int[] outputCells = new int[16];
for (int i = 0; i < 4; i++) {
int[] row = {cells[i * 4], cells[i * 4 + 1], cells[i * 4 + 2], cells[i * 4 + 3]};
outputCells[i * 4] = MULT14[row[0]] ^ MULT11[row[1]] ^ MULT13[row[2]] ^ MULT9[row[3]];
outputCells[i * 4 + 1] = MULT9[row[0]] ^ MULT14[row[1]] ^ MULT11[row[2]] ^ MULT13[row[3]];
outputCells[i * 4 + 2] = MULT13[row[0]] ^ MULT9[row[1]] ^ MULT14[row[2]] ^ MULT11[row[3]];
outputCells[i * 4 + 3] = MULT11[row[0]] ^ MULT13[row[1]] ^ MULT9[row[2]] ^ MULT14[row[3]];
}
return mergeCellsIntoBlock(outputCells);
}
/**
* Encrypts the plaintext with the key and returns the result
*
* @param plainText which we want to encrypt
* @param key the key for encrypt
* @return EncryptedText
*/
public static BigInteger encrypt(BigInteger plainText, BigInteger key) {
BigInteger[] roundKeys = keyExpansion(key);
// Initial round
plainText = addRoundKey(plainText, roundKeys[0]);
// Main rounds
for (int i = 1; i < 10; i++) {
plainText = subBytes(plainText);
plainText = shiftRows(plainText);
plainText = mixColumns(plainText);
plainText = addRoundKey(plainText, roundKeys[i]);
}
// Final round
plainText = subBytes(plainText);
plainText = shiftRows(plainText);
plainText = addRoundKey(plainText, roundKeys[10]);
return plainText;
}
/**
* Decrypts the ciphertext with the key and returns the result
*
* @param cipherText The Encrypted text which we want to decrypt
* @return decryptedText
*/
public static BigInteger decrypt(BigInteger cipherText, BigInteger key) {
BigInteger[] roundKeys = keyExpansion(key);
// Invert final round
cipherText = addRoundKey(cipherText, roundKeys[10]);
cipherText = shiftRowsDec(cipherText);
cipherText = subBytesDec(cipherText);
// Invert main rounds
for (int i = 9; i > 0; i--) {
cipherText = addRoundKey(cipherText, roundKeys[i]);
cipherText = mixColumnsDec(cipherText);
cipherText = shiftRowsDec(cipherText);
cipherText = subBytesDec(cipherText);
}
// Invert initial round
cipherText = addRoundKey(cipherText, roundKeys[0]);
return cipherText;
}
public static void main(String[] args) {
try (Scanner input = new Scanner(System.in)) {
System.out.println("Enter (e) letter for encrpyt or (d) letter for decrypt :");
char choice = input.nextLine().charAt(0);
String in;
switch (choice) {
case 'E', 'e' -> {
System.out.println("Choose a plaintext block (128-Bit Integer in base 16):");
in = input.nextLine();
BigInteger plaintext = new BigInteger(in, 16);
System.out.println("Choose a Key (128-Bit Integer in base 16):");
in = input.nextLine();
BigInteger encryptionKey = new BigInteger(in, 16);
System.out.println(
"The encrypted message is: \n" + encrypt(plaintext, encryptionKey).toString(16));
}
case 'D', 'd' -> {
System.out.println("Enter your ciphertext block (128-Bit Integer in base 16):");
in = input.nextLine();
BigInteger ciphertext = new BigInteger(in, 16);
System.out.println("Choose a Key (128-Bit Integer in base 16):");
in = input.nextLine();
BigInteger decryptionKey = new BigInteger(in, 16);
System.out.println(
"The deciphered message is:\n" + decrypt(ciphertext, decryptionKey).toString(16));
}
default ->
System.out.println("** End **");
}
}
}
}

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src/main/java/com/thealgorithms/ciphers/AESEncryption.java Normal file
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package com.thealgorithms.ciphers;
import javax.crypto.*;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
/**
* This example program shows how AES encryption and decryption can be done in
* Java. Please note that secret key and encrypted text is unreadable binary and
* hence in the following program we display it in hexadecimal format of the
* underlying bytes.
*/
public class AESEncryption {
private static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
/**
* 1. Generate a plain text for encryption 2. Get a secret key (printed in
* hexadecimal form). In actual use this must by encrypted and kept safe.
* The same key is required for decryption.
*/
public static void main(String[] args) throws Exception {
String plainText = "Hello World";
SecretKey secKey = getSecretEncryptionKey();
byte[] cipherText = encryptText(plainText, secKey);
String decryptedText = decryptText(cipherText, secKey);
System.out.println("Original Text:" + plainText);
System.out.println("AES Key (Hex Form):" + bytesToHex(secKey.getEncoded()));
System.out.println("Encrypted Text (Hex Form):" + bytesToHex(cipherText));
System.out.println("Descrypted Text:" + decryptedText);
}
/**
* gets the AES encryption key. In your actual programs, this should be
* safely stored.
*
* @return secKey (Secret key that we encrypt using it)
* @throws NoSuchAlgorithmException (from KeyGenrator)
*/
public static SecretKey getSecretEncryptionKey() throws NoSuchAlgorithmException {
KeyGenerator aesKeyGenerator = KeyGenerator.getInstance("AES");
aesKeyGenerator.init(128); // The AES key size in number of bits
return aesKeyGenerator.generateKey();
}
/**
* Encrypts plainText in AES using the secret key
*
* @return byteCipherText (The encrypted text)
* @throws NoSuchPaddingException (from Cipher)
* @throws NoSuchAlgorithmException (from Cipher)
* @throws InvalidKeyException (from Cipher)
* @throws BadPaddingException (from Cipher)
* @throws IllegalBlockSizeException (from Cipher)
*/
public static byte[] encryptText(String plainText, SecretKey secKey)
throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException,
IllegalBlockSizeException, BadPaddingException {
// AES defaults to AES/ECB/PKCS5Padding in Java 7
Cipher aesCipher = Cipher.getInstance("AES");
aesCipher.init(Cipher.ENCRYPT_MODE, secKey);
return aesCipher.doFinal(plainText.getBytes());
}
/**
* Decrypts encrypted byte array using the key used for encryption.
*
* @return plainText
*/
public static String decryptText(byte[] byteCipherText, SecretKey secKey)
throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException,
IllegalBlockSizeException, BadPaddingException {
// AES defaults to AES/ECB/PKCS5Padding in Java 7
Cipher aesCipher = Cipher.getInstance("AES");
aesCipher.init(Cipher.DECRYPT_MODE, secKey);
byte[] bytePlainText = aesCipher.doFinal(byteCipherText);
return new String(bytePlainText);
}
/**
* Convert a binary byte array into readable hex form Old library is
* deprecated on OpenJdk 11 and this is faster regarding other solution is
* using StringBuilder
*
* @return hexHash
*/
public static String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for (int j = 0; j < bytes.length; j++) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = HEX_ARRAY[v >>> 4];
hexChars[j * 2 + 1] = HEX_ARRAY[v & 0x0F];
}
return new String(hexChars);
}
}

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package com.thealgorithms.ciphers;
class AffineCipher {
// Key values of a and b
static int a = 17;
static int b = 20;
static String encryptMessage(char[] msg) {
/// Cipher Text initially empty
String cipher = "";
for (int i = 0; i < msg.length; i++) {
// Avoid space to be encrypted
/* applying encryption formula ( a x + b ) mod m
{here x is msg[i] and m is 26} and added 'A' to
bring it in range of ascii alphabet[ 65-90 | A-Z ] */
if (msg[i] != ' ') {
cipher = cipher
+ (char) ((((a * (msg[i] - 'A')) + b) % 26) + 'A');
} else // else simply append space character
{
cipher += msg[i];
}
}
return cipher;
}
static String decryptCipher(String cipher) {
String msg = "";
int a_inv = 0;
int flag = 0;
//Find a^-1 (the multiplicative inverse of a
//in the group of integers modulo m.)
for (int i = 0; i < 26; i++) {
flag = (a * i) % 26;
// Check if (a*i)%26 == 1,
// then i will be the multiplicative inverse of a
if (flag == 1) {
a_inv = i;
}
}
for (int i = 0; i < cipher.length(); i++) {
/*Applying decryption formula a^-1 ( x - b ) mod m
{here x is cipher[i] and m is 26} and added 'A'
to bring it in range of ASCII alphabet[ 65-90 | A-Z ] */
if (cipher.charAt(i) != ' ') {
msg = msg + (char) (((a_inv
* ((cipher.charAt(i) + 'A' - b)) % 26)) + 'A');
} else //else simply append space character
{
msg += cipher.charAt(i);
}
}
return msg;
}
// Driver code
public static void main(String[] args) {
String msg = "AFFINE CIPHER";
// Calling encryption function
String cipherText = encryptMessage(msg.toCharArray());
System.out.println("Encrypted Message is : " + cipherText);
// Calling Decryption function
System.out.println("Decrypted Message is: " + decryptCipher(cipherText));
}
}

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src/main/java/com/thealgorithms/ciphers/Caesar.java Normal file
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package com.thealgorithms.ciphers;
import java.util.Scanner;
/**
* A Java implementation of Caesar Cipher. /It is a type of substitution cipher
* in which each letter in the plaintext is replaced by a letter some fixed
* number of positions down the alphabet. /
*
* @author FAHRI YARDIMCI
* @author khalil2535
*/
public class Caesar {
/**
* Encrypt text by shifting every Latin char by add number shift for ASCII
* Example : A + 1 -> B
*
* @return Encrypted message
*/
public static String encode(String message, int shift) {
StringBuilder encoded = new StringBuilder();
shift %= 26;
final int length = message.length();
for (int i = 0; i < length; i++) {
// int current = message.charAt(i); //using char to shift characters because ascii
// is in-order latin alphabet
char current = message.charAt(i); // Java law : char + int = char
if (IsCapitalLatinLetter(current)) {
current += shift;
encoded.append((char) (current > 'Z' ? current - 26 : current)); // 26 = number of latin letters
} else if (IsSmallLatinLetter(current)) {
current += shift;
encoded.append((char) (current > 'z' ? current - 26 : current)); // 26 = number of latin letters
} else {
encoded.append(current);
}
}
return encoded.toString();
}
/**
* Decrypt message by shifting back every Latin char to previous the ASCII
* Example : B - 1 -> A
*
* @return message
*/
public static String decode(String encryptedMessage, int shift) {
StringBuilder decoded = new StringBuilder();
shift %= 26;
final int length = encryptedMessage.length();
for (int i = 0; i < length; i++) {
char current = encryptedMessage.charAt(i);
if (IsCapitalLatinLetter(current)) {
current -= shift;
decoded.append((char) (current < 'A' ? current + 26 : current)); // 26 = number of latin letters
} else if (IsSmallLatinLetter(current)) {
current -= shift;
decoded.append((char) (current < 'a' ? current + 26 : current)); // 26 = number of latin letters
} else {
decoded.append(current);
}
}
return decoded.toString();
}
/**
* @return true if character is capital Latin letter or false for others
*/
private static boolean IsCapitalLatinLetter(char c) {
return c >= 'A' && c <= 'Z';
}
/**
* @return true if character is small Latin letter or false for others
*/
private static boolean IsSmallLatinLetter(char c) {
return c >= 'a' && c <= 'z';
}
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Please enter the message (Latin Alphabet)");
String message = input.nextLine();
System.out.println(message);
System.out.println("Please enter the shift number");
int shift = input.nextInt() % 26;
System.out.println("(E)ncode or (D)ecode ?");
char choice = input.next().charAt(0);
switch (choice) {
case 'E':
case 'e':
System.out.println(
"ENCODED MESSAGE IS \n" + encode(message, shift)); // send our function to handle
break;
case 'D':
case 'd':
System.out.println("DECODED MESSAGE IS \n" + decode(message, shift));
default:
System.out.println("default case");
}
input.close();
}
}

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src/main/java/com/thealgorithms/ciphers/ColumnarTranspositionCipher.java Normal file
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package com.thealgorithms.ciphers;
import java.util.Objects;
/**
* Columnar Transposition Cipher Encryption and Decryption.
*
* @author <a href="https://github.com/freitzzz">freitzzz</a>
*/
public class ColumnarTranspositionCipher {
private static String keyword;
private static Object[][] table;
private static String abecedarium;
public static final String ABECEDARIUM
= "abcdefghijklmnopqrstuvwxyzABCDEFG" + "HIJKLMNOPQRSTUVWXYZ0123456789,.;:-@";
private static final String ENCRYPTION_FIELD = "≈";
private static final char ENCRYPTION_FIELD_CHAR = '≈';
/**
* Encrypts a certain String with the Columnar Transposition Cipher Rule
*
* @param word Word being encrypted
* @param keyword String with keyword being used
* @return a String with the word encrypted by the Columnar Transposition
* Cipher Rule
*/
public static String encrpyter(String word, String keyword) {
ColumnarTranspositionCipher.keyword = keyword;
abecedariumBuilder(500);
table = tableBuilder(word);
Object[][] sortedTable = sortTable(table);
StringBuilder wordEncrypted = new StringBuilder();
for (int i = 0; i < sortedTable[i].length; i++) {
for (int j = 1; j < sortedTable.length; j++) {
wordEncrypted.append(sortedTable[j][i]);
}
}
return wordEncrypted.toString();
}
/**
* Encrypts a certain String with the Columnar Transposition Cipher Rule
*
* @param word Word being encrypted
* @param keyword String with keyword being used
* @param abecedarium String with the abecedarium being used. null for
* default one
* @return a String with the word encrypted by the Columnar Transposition
* Cipher Rule
*/
public static String encrpyter(String word, String keyword, String abecedarium) {
ColumnarTranspositionCipher.keyword = keyword;
ColumnarTranspositionCipher.abecedarium = Objects.requireNonNullElse(abecedarium, ABECEDARIUM);
table = tableBuilder(word);
Object[][] sortedTable = sortTable(table);
StringBuilder wordEncrypted = new StringBuilder();
for (int i = 0; i < sortedTable[0].length; i++) {
for (int j = 1; j < sortedTable.length; j++) {
wordEncrypted.append(sortedTable[j][i]);
}
}
return wordEncrypted.toString();
}
/**
* Decrypts a certain encrypted String with the Columnar Transposition
* Cipher Rule
*
* @return a String decrypted with the word encrypted by the Columnar
* Transposition Cipher Rule
*/
public static String decrypter() {
StringBuilder wordDecrypted = new StringBuilder();
for (int i = 1; i < table.length; i++) {
for (Object item : table[i]) {
wordDecrypted.append(item);
}
}
return wordDecrypted.toString().replaceAll(ENCRYPTION_FIELD, "");
}
/**
* Builds a table with the word to be encrypted in rows by the Columnar
* Transposition Cipher Rule
*
* @return An Object[][] with the word to be encrypted filled in rows and
* columns
*/
private static Object[][] tableBuilder(String word) {
Object[][] table = new Object[numberOfRows(word) + 1][keyword.length()];
char[] wordInChards = word.toCharArray();
// Fils in the respective numbers
table[0] = findElements();
int charElement = 0;
for (int i = 1; i < table.length; i++) {
for (int j = 0; j < table[i].length; j++) {
if (charElement < wordInChards.length) {
table[i][j] = wordInChards[charElement];
charElement++;
} else {
table[i][j] = ENCRYPTION_FIELD_CHAR;
}
}
}
return table;
}
/**
* Determines the number of rows the table should have regarding the
* Columnar Transposition Cipher Rule
*
* @return an int with the number of rows that the table should have in
* order to respect the Columnar Transposition Cipher Rule.
*/
private static int numberOfRows(String word) {
if (word.length() / keyword.length() > word.length() / keyword.length()) {
return (word.length() / keyword.length()) + 1;
} else {
return word.length() / keyword.length();
}
}
/**
* @return charValues
*/
private static Object[] findElements() {
Object[] charValues = new Object[keyword.length()];
for (int i = 0; i < charValues.length; i++) {
int charValueIndex = abecedarium.indexOf(keyword.charAt(i));
charValues[i] = charValueIndex > -1 ? charValueIndex : null;
}
return charValues;
}
/**
* @return tableSorted
*/
private static Object[][] sortTable(Object[][] table) {
Object[][] tableSorted = new Object[table.length][table[0].length];
for (int i = 0; i < tableSorted.length; i++) {
System.arraycopy(table[i], 0, tableSorted[i], 0, tableSorted[i].length);
}
for (int i = 0; i < tableSorted[0].length; i++) {
for (int j = i + 1; j < tableSorted[0].length; j++) {
if ((int) tableSorted[0][i] > (int) table[0][j]) {
Object[] column = getColumn(tableSorted, tableSorted.length, i);
switchColumns(tableSorted, j, i, column);
}
}
}
return tableSorted;
}
/**
* @return columnArray
*/
private static Object[] getColumn(Object[][] table, int rows, int column) {
Object[] columnArray = new Object[rows];
for (int i = 0; i < rows; i++) {
columnArray[i] = table[i][column];
}
return columnArray;
}
private static void switchColumns(
Object[][] table, int firstColumnIndex, int secondColumnIndex, Object[] columnToSwitch) {
for (int i = 0; i < table.length; i++) {
table[i][secondColumnIndex] = table[i][firstColumnIndex];
table[i][firstColumnIndex] = columnToSwitch[i];
}
}
/**
* Creates an abecedarium with a specified ascii inded
*
* @param value Number of characters being used based on the ASCII Table
*/
private static void abecedariumBuilder(int value) {
StringBuilder t = new StringBuilder();
for (int i = 0; i < value; i++) {
t.append((char) i);
}
abecedarium = t.toString();
}
private static void showTable() {
for (Object[] table1 : table) {
for (Object item : table1) {
System.out.print(item + " ");
}
System.out.println();
}
}
public static void main(String[] args) {
String keywordForExample = "asd215";
String wordBeingEncrypted = "This is a test of the Columnar Transposition Cipher";
System.out.println("### Example of Columnar Transposition Cipher ###\n");
System.out.println("Word being encryped ->>> " + wordBeingEncrypted);
System.out.println(
"Word encrypted ->>> "
+ ColumnarTranspositionCipher.encrpyter(wordBeingEncrypted, keywordForExample));
System.out.println("Word decryped ->>> " + ColumnarTranspositionCipher.decrypter());
System.out.println("\n### Encrypted Table ###");
showTable();
}
}

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src/main/java/com/thealgorithms/ciphers/HillCipher.java Normal file
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package com.thealgorithms.ciphers;
import java.util.Scanner;
/*
* Java Implementation of Hill Cipher
* Hill cipher is a polyalphabetic substitution cipher. Each letter is represented by a number belonging to the set Z26 where A=0 , B=1, ..... Z=25.
* To encrypt a message, each block of n letters (since matrix size is n x n) is multiplied by an invertible n × n matrix, against modulus 26.
* To decrypt the message, each block is multiplied by the inverse of the matrix used for encryption.
* The cipher key and plaintext/ciphertext are user inputs.
* @author Ojasva Jain
*/
public class HillCipher {
static Scanner in = new Scanner(System.in);
/* Following function encrypts the message
*/
static void encrypt(String message) {
message = message.toUpperCase();
// Get key matrix
System.out.println("Enter key matrix size");
int n = in.nextInt();
System.out.println("Enter Key/encryptionKey matrix ");
int keyMatrix[][] = new int[n][n];
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
keyMatrix[i][j] = in.nextInt();
}
}
//check if det = 0
if (determinant(keyMatrix, n) % 26 == 0) {
System.out.println("Invalid key, as determinant = 0. Program Terminated");
return;
}
int[][] messageVector = new int[n][1];
String CipherText = "";
int cipherMatrix[][] = new int[n][1];
int j = 0;
while (j < message.length()) {
for (int i = 0; i < n; i++) {
if (j >= message.length()) {
messageVector[i][0] = 23;
} else {
messageVector[i][0] = (message.charAt(j)) % 65;
}
System.out.println(messageVector[i][0]);
j++;
}
int x, i;
for (i = 0; i < n; i++) {
cipherMatrix[i][0] = 0;
for (x = 0; x < n; x++) {
cipherMatrix[i][0] += keyMatrix[i][x] * messageVector[x][0];
}
System.out.println(cipherMatrix[i][0]);
cipherMatrix[i][0] = cipherMatrix[i][0] % 26;
}
for (i = 0; i < n; i++) {
CipherText += (char) (cipherMatrix[i][0] + 65);
}
}
System.out.println("Ciphertext: " + CipherText);
}
//Following function decrypts a message
static void decrypt(String message) {
message = message.toUpperCase();
// Get key matrix
System.out.println("Enter key matrix size");
int n = in.nextInt();
System.out.println("Enter inverseKey/decryptionKey matrix ");
int keyMatrix[][] = new int[n][n];
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
keyMatrix[i][j] = in.nextInt();
}
}
//check if det = 0
if (determinant(keyMatrix, n) % 26 == 0) {
System.out.println("Invalid key, as determinant = 0. Program Terminated");
return;
}
//solving for the required plaintext message
int[][] messageVector = new int[n][1];
String PlainText = "";
int plainMatrix[][] = new int[n][1];
int j = 0;
while (j < message.length()) {
for (int i = 0; i < n; i++) {
if (j >= message.length()) {
messageVector[i][0] = 23;
} else {
messageVector[i][0] = (message.charAt(j)) % 65;
}
System.out.println(messageVector[i][0]);
j++;
}
int x, i;
for (i = 0; i < n; i++) {
plainMatrix[i][0] = 0;
for (x = 0; x < n; x++) {
plainMatrix[i][0] += keyMatrix[i][x] * messageVector[x][0];
}
plainMatrix[i][0] = plainMatrix[i][0] % 26;
}
for (i = 0; i < n; i++) {
PlainText += (char) (plainMatrix[i][0] + 65);
}
}
System.out.println("Plaintext: " + PlainText);
}
// Determinant calculator
public static int determinant(int a[][], int n) {
int det = 0, sign = 1, p = 0, q = 0;
if (n == 1) {
det = a[0][0];
} else {
int b[][] = new int[n - 1][n - 1];
for (int x = 0; x < n; x++) {
p = 0;
q = 0;
for (int i = 1; i < n; i++) {
for (int j = 0; j < n; j++) {
if (j != x) {
b[p][q++] = a[i][j];
if (q % (n - 1) == 0) {
p++;
q = 0;
}
}
}
}
det = det + a[0][x] * determinant(b, n - 1) * sign;
sign = -sign;
}
}
return det;
}
// Function to implement Hill Cipher
static void hillcipher(String message) {
message.toUpperCase();
System.out.println("What do you want to process from the message?");
System.out.println("Press 1: To Encrypt");
System.out.println("Press 2: To Decrypt");
short sc = in.nextShort();
if (sc == 1) {
encrypt(message);
} else if (sc == 2) {
decrypt(message);
} else {
System.out.println("Invalid input, program terminated.");
}
}
// Driver code
public static void main(String[] args) {
// Get the message to be encrypted
System.out.println("Enter message");
String message = in.nextLine();
hillcipher(message);
}
}

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src/main/java/com/thealgorithms/ciphers/ProductCipher.java Normal file
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package com.thealgorithms.ciphers;
import java.util.Scanner;
class ProductCipher {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter the input to be encrypted: ");
String substitutionInput = sc.nextLine();
System.out.println(" ");
System.out.println("Enter a number: ");
int n = sc.nextInt();
// Substitution encryption
StringBuffer substitutionOutput = new StringBuffer();
for (int i = 0; i < substitutionInput.length(); i++) {
char c = substitutionInput.charAt(i);
substitutionOutput.append((char) (c + 5));
}
System.out.println(" ");
System.out.println("Substituted text: ");
System.out.println(substitutionOutput);
// Transposition encryption
String transpositionInput = substitutionOutput.toString();
int modulus;
if ((modulus = transpositionInput.length() % n) != 0) {
modulus = n - modulus;
for (; modulus != 0; modulus--) {
transpositionInput += "/";
}
}
StringBuffer transpositionOutput = new StringBuffer();
System.out.println(" ");
System.out.println("Transposition Matrix: ");
for (int i = 0; i < n; i++) {
for (int j = 0; j < transpositionInput.length() / n; j++) {
char c = transpositionInput.charAt(i + (j * n));
System.out.print(c);
transpositionOutput.append(c);
}
System.out.println();
}
System.out.println(" ");
System.out.println("Final encrypted text: ");
System.out.println(transpositionOutput);
// Transposition decryption
n = transpositionOutput.length() / n;
StringBuffer transpositionPlaintext = new StringBuffer();
for (int i = 0; i < n; i++) {
for (int j = 0; j < transpositionOutput.length() / n; j++) {
char c = transpositionOutput.charAt(i + (j * n));
transpositionPlaintext.append(c);
}
}
// Substitution decryption
StringBuffer plaintext = new StringBuffer();
for (int i = 0; i < transpositionPlaintext.length(); i++) {
char c = transpositionPlaintext.charAt(i);
plaintext.append((char) (c - 5));
}
System.out.println("Plaintext: ");
System.out.println(plaintext);
sc.close();
}
}

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src/main/java/com/thealgorithms/ciphers/RSA.java Normal file
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package com.thealgorithms.ciphers;
import javax.swing.*;
import java.math.BigInteger;
import java.security.SecureRandom;
/**
* @author Nguyen Duy Tiep on 23-Oct-17.
*/
public final class RSA {
public static void main(String[] args) {
RSA rsa = new RSA(1024);
String text1 = JOptionPane.showInputDialog("Enter a message to encrypt :");
String ciphertext = rsa.encrypt(text1);
JOptionPane.showMessageDialog(null, "Your encrypted message : " + ciphertext);
JOptionPane.showMessageDialog(null, "Your message after decrypt : " + rsa.decrypt(ciphertext));
}
private BigInteger modulus, privateKey, publicKey;
public RSA(int bits) {
generateKeys(bits);
}
/**
* @return encrypted message
*/
public synchronized String encrypt(String message) {
return (new BigInteger(message.getBytes())).modPow(publicKey, modulus).toString();
}
/**
* @return encrypted message as big integer
*/
public synchronized BigInteger encrypt(BigInteger message) {
return message.modPow(publicKey, modulus);
}
/**
* @return plain message
*/
public synchronized String decrypt(String encryptedMessage) {
return new String((new BigInteger(encryptedMessage)).modPow(privateKey, modulus).toByteArray());
}
/**
* @return plain message as big integer
*/
public synchronized BigInteger decrypt(BigInteger encryptedMessage) {
return encryptedMessage.modPow(privateKey, modulus);
}
/**
* Generate a new public and private key set.
*/
public synchronized void generateKeys(int bits) {
SecureRandom r = new SecureRandom();
BigInteger p = new BigInteger(bits / 2, 100, r);
BigInteger q = new BigInteger(bits / 2, 100, r);
modulus = p.multiply(q);
BigInteger m = (p.subtract(BigInteger.ONE)).multiply(q.subtract(BigInteger.ONE));
publicKey = new BigInteger("3");
while (m.gcd(publicKey).intValue() > 1) {
publicKey = publicKey.add(new BigInteger("2"));
}
privateKey = publicKey.modInverse(m);
}
}

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src/main/java/com/thealgorithms/ciphers/SimpleSubCipher.java Normal file
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package com.thealgorithms.ciphers;
import java.util.HashMap;
import java.util.Map;
/**
* The simple substitution cipher is a cipher that has been in use for many
* hundreds of years (an excellent history is given in Simon Singhs 'the Code
* Book'). It basically consists of substituting every plaintext character for a
* different ciphertext character. It differs from the Caesar cipher in that the
* cipher alphabet is not simply the alphabet shifted, it is completely jumbled.
*/
public class SimpleSubCipher {
/**
* Encrypt text by replacing each element with its opposite character.
*
* @param message
* @param cipherSmall
* @return Encrypted message
*/
public static String encode(String message, String cipherSmall) {
String encoded = "";
// This map is used to encode
Map<Character, Character> cipherMap = new HashMap<>();
char beginSmallLetter = 'a';
char beginCapitalLetter = 'A';
cipherSmall = cipherSmall.toLowerCase();
String cipherCapital = cipherSmall.toUpperCase();
// To handle Small and Capital letters
for (int i = 0; i < cipherSmall.length(); i++) {
cipherMap.put(beginSmallLetter++, cipherSmall.charAt(i));
cipherMap.put(beginCapitalLetter++, cipherCapital.charAt(i));
}
for (int i = 0; i < message.length(); i++) {
if (Character.isAlphabetic(message.charAt(i))) {
encoded += cipherMap.get(message.charAt(i));
} else {
encoded += message.charAt(i);
}
}
return encoded;
}
/**
* Decrypt message by replacing each element with its opposite character in
* cipher.
*
* @param encryptedMessage
* @param cipherSmall
* @return message
*/
public static String decode(String encryptedMessage, String cipherSmall) {
String decoded = "";
Map<Character, Character> cipherMap = new HashMap<Character, Character>();
char beginSmallLetter = 'a';
char beginCapitalLetter = 'A';
cipherSmall = cipherSmall.toLowerCase();
String cipherCapital = cipherSmall.toUpperCase();
for (int i = 0; i < cipherSmall.length(); i++) {
cipherMap.put(cipherSmall.charAt(i), beginSmallLetter++);
cipherMap.put(cipherCapital.charAt(i), beginCapitalLetter++);
}
for (int i = 0; i < encryptedMessage.length(); i++) {
if (Character.isAlphabetic(encryptedMessage.charAt(i))) {
decoded += cipherMap.get(encryptedMessage.charAt(i));
} else {
decoded += encryptedMessage.charAt(i);
}
}
return decoded;
}
public static void main(String[] args) {
String a = encode("defend the east wall of the castle", "phqgiumeaylnofdxjkrcvstzwb");
String b = decode(a, "phqgiumeaylnofdxjkrcvstzwb");
System.out.println(b);
}
}

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src/main/java/com/thealgorithms/ciphers/SimpleSubstitutionCipher.java Normal file
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package com.thealgorithms.ciphers;
import java.util.HashMap;
import java.util.Map;
/**
* The simple substitution cipher is a cipher that has been in use for many
* hundreds of years (an excellent history is given in Simon Singhs 'the Code
* Book'). It basically consists of substituting every plaintext character for a
* different ciphertext character. It differs from the Caesar cipher in that the
* cipher alphabet is not simply the alphabet shifted, it is completely jumbled.
*
* @author Hassan Elseoudy
*/
public class SimpleSubstitutionCipher {
/**
* Encrypt text by replacing each element with its opposite character.
*
* @return Encrypted message
*/
public static String encode(String message, String cipherSmall) {
StringBuilder encoded = new StringBuilder();
// This map is used to encode
Map<Character, Character> cipherMap = new HashMap<>();
char beginSmallLetter = 'a';
char beginCapitalLetter = 'A';
cipherSmall = cipherSmall.toLowerCase();
String cipherCapital = cipherSmall.toUpperCase();
// To handle Small and Capital letters
for (int i = 0; i < cipherSmall.length(); i++) {
cipherMap.put(beginSmallLetter++, cipherSmall.charAt(i));
cipherMap.put(beginCapitalLetter++, cipherCapital.charAt(i));
}
for (int i = 0; i < message.length(); i++) {
if (Character.isAlphabetic(message.charAt(i))) {
encoded.append(cipherMap.get(message.charAt(i)));
} else {
encoded.append(message.charAt(i));
}
}
return encoded.toString();
}
/**
* Decrypt message by replacing each element with its opposite character in
* cipher.
*
* @return message
*/
public static String decode(String encryptedMessage, String cipherSmall) {
StringBuilder decoded = new StringBuilder();
Map<Character, Character> cipherMap = new HashMap<>();
char beginSmallLetter = 'a';
char beginCapitalLetter = 'A';
cipherSmall = cipherSmall.toLowerCase();
String cipherCapital = cipherSmall.toUpperCase();
for (int i = 0; i < cipherSmall.length(); i++) {
cipherMap.put(cipherSmall.charAt(i), beginSmallLetter++);
cipherMap.put(cipherCapital.charAt(i), beginCapitalLetter++);
}
for (int i = 0; i < encryptedMessage.length(); i++) {
if (Character.isAlphabetic(encryptedMessage.charAt(i))) {
decoded.append(cipherMap.get(encryptedMessage.charAt(i)));
} else {
decoded.append(encryptedMessage.charAt(i));
}
}
return decoded.toString();
}
/**
* TODO remove main and make JUnit Testing
*/
public static void main(String[] args) {
String a = encode("defend the east wall of the castle", "phqgiumeaylnofdxjkrcvstzwb");
String b = decode(a, "phqgiumeaylnofdxjkrcvstzwb");
System.out.println(b);
}
}

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src/main/java/com/thealgorithms/ciphers/Vigenere.java Normal file
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package com.thealgorithms.ciphers;
/**
* A Java implementation of Vigenere Cipher.
*
* @author straiffix
* @author beingmartinbmc
*/
public class Vigenere {
public static String encrypt(final String message, final String key) {
StringBuilder result = new StringBuilder();
for (int i = 0, j = 0; i < message.length(); i++) {
char c = message.charAt(i);
if (Character.isLetter(c)) {
if (Character.isUpperCase(c)) {
result.append((char) ((c + key.toUpperCase().charAt(j) - 2 * 'A') % 26 + 'A'));
} else {
result.append((char) ((c + key.toLowerCase().charAt(j) - 2 * 'a') % 26 + 'a'));
}
} else {
result.append(c);
}
j = ++j % key.length();
}
return result.toString();
}
public static String decrypt(final String message, final String key) {
StringBuilder result = new StringBuilder();
for (int i = 0, j = 0; i < message.length(); i++) {
char c = message.charAt(i);
if (Character.isLetter(c)) {
if (Character.isUpperCase(c)) {
result.append((char) ('Z' - (25 - (c - key.toUpperCase().charAt(j))) % 26));
} else {
result.append((char) ('z' - (25 - (c - key.toLowerCase().charAt(j))) % 26));
}
} else {
result.append(c);
}
j = ++j % key.length();
}
return result.toString();
}
public static void main(String[] args) {
String text = "Hello World!";
String key = "itsakey";
System.out.println(text);
String ciphertext = encrypt(text, key);
System.out.println(ciphertext);
System.out.println(decrypt(ciphertext, key));
}
}