diff options
Diffstat (limited to 'bcprov/src/main/java/org/bouncycastle/crypto/ec/ECElGamalDecryptor.java')
-rw-r--r-- | bcprov/src/main/java/org/bouncycastle/crypto/ec/ECElGamalDecryptor.java | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/bcprov/src/main/java/org/bouncycastle/crypto/ec/ECElGamalDecryptor.java b/bcprov/src/main/java/org/bouncycastle/crypto/ec/ECElGamalDecryptor.java new file mode 100644 index 0000000..2f1c937 --- /dev/null +++ b/bcprov/src/main/java/org/bouncycastle/crypto/ec/ECElGamalDecryptor.java @@ -0,0 +1,48 @@ +package org.bouncycastle.crypto.ec; + +import org.bouncycastle.crypto.CipherParameters; +import org.bouncycastle.crypto.params.ECPrivateKeyParameters; +import org.bouncycastle.math.ec.ECPoint; + +/** + * this does your basic decryption ElGamal style using EC + */ +public class ECElGamalDecryptor + implements ECDecryptor +{ + private ECPrivateKeyParameters key; + + /** + * initialise the decryptor. + * + * @param param the necessary EC key parameters. + */ + public void init( + CipherParameters param) + { + if (!(param instanceof ECPrivateKeyParameters)) + { + throw new IllegalArgumentException("ECPrivateKeyParameters are required for decryption."); + } + + this.key = (ECPrivateKeyParameters)param; + } + + /** + * Decrypt an EC pair producing the original EC point. + * + * @param pair the EC point pair to process. + * @return the result of the Elgamal process. + */ + public ECPoint decrypt(ECPair pair) + { + if (key == null) + { + throw new IllegalStateException("ECElGamalDecryptor not initialised"); + } + + ECPoint tmp = pair.getX().multiply(key.getD()); + + return pair.getY().subtract(tmp).normalize(); + } +} |