From c56d282ae092810327bc18b6083d552a91b9eb8e Mon Sep 17 00:00:00 2001 From: Ritisha Pande <96540421+riti2601@users.noreply.github.com> Date: Tue, 22 Oct 2024 23:46:35 +0530 Subject: [PATCH] Add DiffieHellman and MonoAlphabetic (#5508) --- .../thealgorithms/ciphers/DiffieHellman.java | 36 ++++++++++++++ .../thealgorithms/ciphers/MonoAlphabetic.java | 48 +++++++++++++++++++ .../ciphers/DiffieHellmanTest.java | 38 +++++++++++++++ .../ciphers/MonoAlphabeticTest.java | 29 +++++++++++ 4 files changed, 151 insertions(+) create mode 100644 src/main/java/com/thealgorithms/ciphers/DiffieHellman.java create mode 100644 src/main/java/com/thealgorithms/ciphers/MonoAlphabetic.java create mode 100644 src/test/java/com/thealgorithms/ciphers/DiffieHellmanTest.java create mode 100644 src/test/java/com/thealgorithms/ciphers/MonoAlphabeticTest.java diff --git a/src/main/java/com/thealgorithms/ciphers/DiffieHellman.java b/src/main/java/com/thealgorithms/ciphers/DiffieHellman.java new file mode 100644 index 000000000..7470b40e0 --- /dev/null +++ b/src/main/java/com/thealgorithms/ciphers/DiffieHellman.java @@ -0,0 +1,36 @@ +package com.thealgorithms.ciphers; + +import java.math.BigInteger; + +public final class DiffieHellman { + + private final BigInteger base; + private final BigInteger secret; + private final BigInteger prime; + + // Constructor to initialize base, secret, and prime + public DiffieHellman(BigInteger base, BigInteger secret, BigInteger prime) { + // Check for non-null and positive values + if (base == null || secret == null || prime == null || base.signum() <= 0 || secret.signum() <= 0 || prime.signum() <= 0) { + throw new IllegalArgumentException("Base, secret, and prime must be non-null and positive values."); + } + this.base = base; + this.secret = secret; + this.prime = prime; + } + + // Method to calculate public value (g^x mod p) + public BigInteger calculatePublicValue() { + // Returns g^x mod p + return base.modPow(secret, prime); + } + + // Method to calculate the shared secret key (otherPublic^secret mod p) + public BigInteger calculateSharedSecret(BigInteger otherPublicValue) { + if (otherPublicValue == null || otherPublicValue.signum() <= 0) { + throw new IllegalArgumentException("Other public value must be non-null and positive."); + } + // Returns b^x mod p or a^y mod p + return otherPublicValue.modPow(secret, prime); + } +} diff --git a/src/main/java/com/thealgorithms/ciphers/MonoAlphabetic.java b/src/main/java/com/thealgorithms/ciphers/MonoAlphabetic.java new file mode 100644 index 000000000..1d5b7110a --- /dev/null +++ b/src/main/java/com/thealgorithms/ciphers/MonoAlphabetic.java @@ -0,0 +1,48 @@ +package com.thealgorithms.ciphers; + +public final class MonoAlphabetic { + + private MonoAlphabetic() { + throw new UnsupportedOperationException("Utility class"); + } + + // Encryption method + public static String encrypt(String data, String key) { + if (!data.matches("[A-Z]+")) { + throw new IllegalArgumentException("Input data contains invalid characters. Only uppercase A-Z are allowed."); + } + StringBuilder sb = new StringBuilder(); + + // Encrypt each character + for (char c : data.toCharArray()) { + int idx = charToPos(c); // Get the index of the character + sb.append(key.charAt(idx)); // Map to the corresponding character in the key + } + return sb.toString(); + } + + // Decryption method + public static String decrypt(String data, String key) { + StringBuilder sb = new StringBuilder(); + + // Decrypt each character + for (char c : data.toCharArray()) { + int idx = key.indexOf(c); // Find the index of the character in the key + if (idx == -1) { + throw new IllegalArgumentException("Input data contains invalid characters."); + } + sb.append(posToChar(idx)); // Convert the index back to the original character + } + return sb.toString(); + } + + // Helper method: Convert a character to its position in the alphabet + private static int charToPos(char c) { + return c - 'A'; // Subtract 'A' to get position (0 for A, 1 for B, etc.) + } + + // Helper method: Convert a position in the alphabet to a character + private static char posToChar(int pos) { + return (char) (pos + 'A'); // Add 'A' to convert position back to character + } +} diff --git a/src/test/java/com/thealgorithms/ciphers/DiffieHellmanTest.java b/src/test/java/com/thealgorithms/ciphers/DiffieHellmanTest.java new file mode 100644 index 000000000..6255ad22a --- /dev/null +++ b/src/test/java/com/thealgorithms/ciphers/DiffieHellmanTest.java @@ -0,0 +1,38 @@ +package com.thealgorithms.ciphers; + +import static org.junit.jupiter.api.Assertions.assertEquals; + +import java.math.BigInteger; +import java.util.stream.Stream; +import org.junit.jupiter.params.ParameterizedTest; +import org.junit.jupiter.params.provider.Arguments; +import org.junit.jupiter.params.provider.MethodSource; + +public class DiffieHellmanTest { + + // Test for public value calculation using instance methods + @ParameterizedTest + @MethodSource("provideTestData") + public void testCalculatePublicValue(BigInteger base, BigInteger secret, BigInteger prime, BigInteger publicExpected, BigInteger sharedExpected) { + DiffieHellman dh = new DiffieHellman(base, secret, prime); // Create an instance of DiffieHellman + assertEquals(publicExpected, dh.calculatePublicValue()); // Call instance method + } + + // Test for shared secret calculation using instance methods + @ParameterizedTest + @MethodSource("provideTestData") + public void testCalculateSharedSecret(BigInteger base, BigInteger secret, BigInteger prime, BigInteger publicExpected, BigInteger sharedExpected) { + DiffieHellman dh = new DiffieHellman(base, secret, prime); // Create an instance of DiffieHellman + assertEquals(sharedExpected, dh.calculateSharedSecret(publicExpected)); // Call instance method + } + + // Provide test data for both public key and shared secret calculation + private static Stream provideTestData() { + return Stream.of(createTestArgs(5, 6, 23, 8, 13), createTestArgs(2, 5, 13, 6, 2)); + } + + // Helper method for arguments + private static Arguments createTestArgs(long base, long secret, long prime, long publicExpected, long sharedExpected) { + return Arguments.of(BigInteger.valueOf(base), BigInteger.valueOf(secret), BigInteger.valueOf(prime), BigInteger.valueOf(publicExpected), BigInteger.valueOf(sharedExpected)); + } +} diff --git a/src/test/java/com/thealgorithms/ciphers/MonoAlphabeticTest.java b/src/test/java/com/thealgorithms/ciphers/MonoAlphabeticTest.java new file mode 100644 index 000000000..b1a8c78c9 --- /dev/null +++ b/src/test/java/com/thealgorithms/ciphers/MonoAlphabeticTest.java @@ -0,0 +1,29 @@ +package com.thealgorithms.ciphers; + +import static org.junit.jupiter.api.Assertions.assertEquals; + +import java.util.stream.Stream; +import org.junit.jupiter.params.ParameterizedTest; +import org.junit.jupiter.params.provider.Arguments; +import org.junit.jupiter.params.provider.MethodSource; + +public class MonoAlphabeticTest { + + // Test for both encryption and decryption with different keys + @ParameterizedTest + @MethodSource("provideTestData") + public void testEncryptDecrypt(String plainText, String key, String encryptedText) { + // Test encryption + String actualEncrypted = MonoAlphabetic.encrypt(plainText, key); + assertEquals(encryptedText, actualEncrypted, "Encryption failed for input: " + plainText + " with key: " + key); + + // Test decryption + String actualDecrypted = MonoAlphabetic.decrypt(encryptedText, key); + assertEquals(plainText, actualDecrypted, "Decryption failed for input: " + encryptedText + " with key: " + key); + } + + // Provide test data for both encryption and decryption + private static Stream provideTestData() { + return Stream.of(Arguments.of("HELLO", "MNBVCXZLKJHGFDSAPOIUYTREWQ", "LCGGS"), Arguments.of("JAVA", "MNBVCXZLKJHGFDSAPOIUYTREWQ", "JMTM"), Arguments.of("HELLO", "QWERTYUIOPLKJHGFDSAZXCVBNM", "ITKKG"), Arguments.of("JAVA", "QWERTYUIOPLKJHGFDSAZXCVBNM", "PQCQ")); + } +}