diff options
author | David Hook <dgh@cryptoworkshop.com> | 2013-05-31 11:07:45 +0400 |
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committer | David Hook <dgh@cryptoworkshop.com> | 2013-05-31 11:07:45 +0400 |
commit | 2b976f5364cfdbc37d3086019d93483c983eb80b (patch) | |
tree | cb846af3fd1d43f9c2562a1fb2d06b997ad8f229 /core/src/main/java/org/bouncycastle/crypto/engines/RSABlindedEngine.java | |
parent | 5f714bd92fbd780d22406f4bc3681be005f6f04a (diff) |
initial reshuffle
Diffstat (limited to 'core/src/main/java/org/bouncycastle/crypto/engines/RSABlindedEngine.java')
-rw-r--r-- | core/src/main/java/org/bouncycastle/crypto/engines/RSABlindedEngine.java | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/core/src/main/java/org/bouncycastle/crypto/engines/RSABlindedEngine.java b/core/src/main/java/org/bouncycastle/crypto/engines/RSABlindedEngine.java new file mode 100644 index 00000000..e7fb9432 --- /dev/null +++ b/core/src/main/java/org/bouncycastle/crypto/engines/RSABlindedEngine.java @@ -0,0 +1,126 @@ +package org.bouncycastle.crypto.engines; + +import org.bouncycastle.crypto.AsymmetricBlockCipher; +import org.bouncycastle.crypto.CipherParameters; +import org.bouncycastle.crypto.DataLengthException; +import org.bouncycastle.crypto.params.ParametersWithRandom; +import org.bouncycastle.crypto.params.RSAKeyParameters; +import org.bouncycastle.crypto.params.RSAPrivateCrtKeyParameters; +import org.bouncycastle.util.BigIntegers; + +import java.math.BigInteger; +import java.security.SecureRandom; + +/** + * this does your basic RSA algorithm with blinding + */ +public class RSABlindedEngine + implements AsymmetricBlockCipher +{ + private static BigInteger ONE = BigInteger.valueOf(1); + + private RSACoreEngine core = new RSACoreEngine(); + private RSAKeyParameters key; + private SecureRandom random; + + /** + * initialise the RSA engine. + * + * @param forEncryption true if we are encrypting, false otherwise. + * @param param the necessary RSA key parameters. + */ + public void init( + boolean forEncryption, + CipherParameters param) + { + core.init(forEncryption, param); + + if (param instanceof ParametersWithRandom) + { + ParametersWithRandom rParam = (ParametersWithRandom)param; + + key = (RSAKeyParameters)rParam.getParameters(); + random = rParam.getRandom(); + } + else + { + key = (RSAKeyParameters)param; + random = new SecureRandom(); + } + } + + /** + * Return the maximum size for an input block to this engine. + * For RSA this is always one byte less than the key size on + * encryption, and the same length as the key size on decryption. + * + * @return maximum size for an input block. + */ + public int getInputBlockSize() + { + return core.getInputBlockSize(); + } + + /** + * Return the maximum size for an output block to this engine. + * For RSA this is always one byte less than the key size on + * decryption, and the same length as the key size on encryption. + * + * @return maximum size for an output block. + */ + public int getOutputBlockSize() + { + return core.getOutputBlockSize(); + } + + /** + * Process a single block using the basic RSA algorithm. + * + * @param in the input array. + * @param inOff the offset into the input buffer where the data starts. + * @param inLen the length of the data to be processed. + * @return the result of the RSA process. + * @exception DataLengthException the input block is too large. + */ + public byte[] processBlock( + byte[] in, + int inOff, + int inLen) + { + if (key == null) + { + throw new IllegalStateException("RSA engine not initialised"); + } + + BigInteger input = core.convertInput(in, inOff, inLen); + + BigInteger result; + if (key instanceof RSAPrivateCrtKeyParameters) + { + RSAPrivateCrtKeyParameters k = (RSAPrivateCrtKeyParameters)key; + + BigInteger e = k.getPublicExponent(); + if (e != null) // can't do blinding without a public exponent + { + BigInteger m = k.getModulus(); + BigInteger r = BigIntegers.createRandomInRange(ONE, m.subtract(ONE), random); + + BigInteger blindedInput = r.modPow(e, m).multiply(input).mod(m); + BigInteger blindedResult = core.processBlock(blindedInput); + + BigInteger rInv = r.modInverse(m); + result = blindedResult.multiply(rInv).mod(m); + } + else + { + result = core.processBlock(input); + } + } + else + { + result = core.processBlock(input); + } + + return core.convertOutput(result); + } +} |