/** * Decrypt an encapsulated session key. * * @param in the input buffer for the encapsulated key. * @param inOff the offset for the input buffer. * @param inLen the length of the encapsulated key. * @param keyLen the length of the session key. * @return the session key. */ public CipherParameters decrypt(byte[] in, int inOff, int inLen, int keyLen) throws IllegalArgumentException { if (!key.isPrivate()) { throw new IllegalArgumentException("Private key required for decryption"); } BigInteger n = key.getModulus(); BigInteger d = key.getExponent(); // Decode the input byte[] C = new byte[inLen]; System.arraycopy(in, inOff, C, 0, C.length); BigInteger c = new BigInteger(1, C); // Decrypt the ephemeral random and encode it BigInteger r = c.modPow(d, n); return generateKey(n, r, keyLen); }
/** * Decrypt an encapsulated session key. * * @param in the input buffer for the encapsulated key. * @param inOff the offset for the input buffer. * @param inLen the length of the encapsulated key. * @param keyLen the length of the session key. * @return the session key. */ public CipherParameters decrypt(byte[] in, int inOff, int inLen, int keyLen) throws IllegalArgumentException { if (!key.isPrivate()) { throw new IllegalArgumentException("Private key required for decryption"); } BigInteger n = key.getModulus(); BigInteger d = key.getExponent(); // Decode the input byte[] C = new byte[inLen]; System.arraycopy(in, inOff, C, 0, C.length); BigInteger c = new BigInteger(1, C); // Decrypt the ephemeral random and encode it BigInteger r = c.modPow(d, n); return generateKey(n, r, keyLen); }
/** * Generate and encapsulate a random session key. * * @param out the output buffer for the encapsulated key. * @param outOff the offset for the output buffer. * @param keyLen the length of the random session key. * @return the random session key. */ public CipherParameters encrypt(byte[] out, int outOff, int keyLen) throws IllegalArgumentException { if (key.isPrivate()) { throw new IllegalArgumentException("Public key required for encryption"); } BigInteger n = key.getModulus(); BigInteger e = key.getExponent(); // Generate the ephemeral random and encode it BigInteger r = BigIntegers.createRandomInRange(ZERO, n.subtract(ONE), rnd); // Encrypt the random and encode it BigInteger c = r.modPow(e, n); byte[] C = BigIntegers.asUnsignedByteArray((n.bitLength() + 7) / 8, c); System.arraycopy(C, 0, out, outOff, C.length); return generateKey(n, r, keyLen); }
/** * Generate and encapsulate a random session key. * * @param out the output buffer for the encapsulated key. * @param outOff the offset for the output buffer. * @param keyLen the length of the random session key. * @return the random session key. */ public CipherParameters encrypt(byte[] out, int outOff, int keyLen) throws IllegalArgumentException { if (key.isPrivate()) { throw new IllegalArgumentException("Public key required for encryption"); } BigInteger n = key.getModulus(); BigInteger e = key.getExponent(); // Generate the ephemeral random and encode it BigInteger r = BigIntegers.createRandomInRange(ZERO, n.subtract(ONE), rnd); // Encrypt the random and encode it BigInteger c = r.modPow(e, n); byte[] C = BigIntegers.asUnsignedByteArray((n.bitLength() + 7) / 8, c); System.arraycopy(C, 0, out, outOff, C.length); return generateKey(n, r, keyLen); }