Package net.i2p.crypto

Class ElGamalEngine

  • public final class ElGamalEngine
extends Object
    Wrapper for ElGamal encryption/signature schemes. Does all of Elgamal now for data sizes of 222 bytes and less. The data to be encrypted is first prepended with a random nonzero byte, then the 32 bytes making up the SHA256 of the data, then the data itself. The random byte and the SHA256 hash is stripped on decrypt so the original data is returned. Not recommended for new applications.
    Author:
    thecrypto, jrandom

    • Constructor Detail

      • ElGamalEngine

        public ElGamalEngine​(I2PAppContext context)
        The ElGamal engine should only be constructed and accessed through the application context. This constructor should only be used by the appropriate application context itself. Starts the YK precalc thread if context is RouterContext or Android.

    • Method Detail

      • shutdown

        public void shutdown()
        Note that this stops the precalc thread and it cannot be restarted.
        Since:
        0.8.8

      • restart

        public void restart()
        This is now a noop. Cannot be restarted.
        Since:
        0.8.8

      • encrypt

        public byte[] encrypt​(byte[] data,
                      PublicKey publicKey)
        encrypt the data to the public key
        Parameters:
        publicKey - public key encrypt to
        data - data to encrypt, must be 222 bytes or less As the encrypted data may contain a substantial number of zeros if the cleartext is smaller than 222 bytes, it is recommended that the caller pad the cleartext to 222 bytes with random data.
        Returns:
        encrypted data, will be exactly 514 bytes long Contains the two-part encrypted data starting at bytes 0 and 257. If the encrypted parts are smaller than 257 bytes, they will be padded with leading zeros. The parts appear to always be 256 bytes or less, in other words, bytes 0 and 257 are always zero.

      • decrypt

        public byte[] decrypt​(byte[] encrypted,
                      PrivateKey privateKey)
        Decrypt the data
        Parameters:
        encrypted - encrypted data, must be exactly 514 bytes Contains the two-part encrypted data starting at bytes 0 and 257. If the encrypted parts are smaller than 257 bytes, they must be padded with leading zeros.
        privateKey - private key to decrypt with
        Returns:
        unencrypted data or null on failure