DiffieHellman.java

packagecom.thealgorithms.ciphers;

importjava.math.BigInteger;

publicfinalclassDiffieHellman {

privatefinalBigIntegerbase;
privatefinalBigIntegersecret;
privatefinalBigIntegerprime;

// Constructor to initialize base, secret, and prime
publicDiffieHellman(BigIntegerbase, BigIntegersecret, BigIntegerprime) {
// Check for non-null and positive values
if (base == null || secret == null || prime == null || base.signum() <= 0 || secret.signum() <= 0 || prime.signum() <= 0) {
thrownewIllegalArgumentException("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)
publicBigIntegercalculatePublicValue() {
// Returns g^x mod p
returnbase.modPow(secret, prime);
 }

// Method to calculate the shared secret key (otherPublic^secret mod p)
publicBigIntegercalculateSharedSecret(BigIntegerotherPublicValue) {
if (otherPublicValue == null || otherPublicValue.signum() <= 0) {
thrownewIllegalArgumentException("Other public value must be non-null and positive.");
 }
// Returns b^x mod p or a^y mod p
returnotherPublicValue.modPow(secret, prime);
 }
}