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236
iTechSharp/srcbc/crypto/engines/IesEngine.cs
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236
iTechSharp/srcbc/crypto/engines/IesEngine.cs
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using System;
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using Org.BouncyCastle.Crypto.Parameters;
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using Org.BouncyCastle.Math;
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namespace Org.BouncyCastle.Crypto.Engines
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{
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/**
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* support class for constructing intergrated encryption ciphers
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* for doing basic message exchanges on top of key agreement ciphers
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*/
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public class IesEngine
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{
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private readonly IBasicAgreement agree;
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private readonly IDerivationFunction kdf;
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private readonly IMac mac;
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private readonly BufferedBlockCipher cipher;
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private readonly byte[] macBuf;
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private bool forEncryption;
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private ICipherParameters privParam, pubParam;
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private IesParameters param;
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/**
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* set up for use with stream mode, where the key derivation function
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* is used to provide a stream of bytes to xor with the message.
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*
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* @param agree the key agreement used as the basis for the encryption
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* @param kdf the key derivation function used for byte generation
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* @param mac the message authentication code generator for the message
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*/
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public IesEngine(
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IBasicAgreement agree,
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IDerivationFunction kdf,
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IMac mac)
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{
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this.agree = agree;
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this.kdf = kdf;
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this.mac = mac;
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this.macBuf = new byte[mac.GetMacSize()];
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// this.cipher = null;
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}
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/**
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* set up for use in conjunction with a block cipher to handle the
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* message.
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*
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* @param agree the key agreement used as the basis for the encryption
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* @param kdf the key derivation function used for byte generation
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* @param mac the message authentication code generator for the message
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* @param cipher the cipher to used for encrypting the message
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*/
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public IesEngine(
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IBasicAgreement agree,
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IDerivationFunction kdf,
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IMac mac,
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BufferedBlockCipher cipher)
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{
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this.agree = agree;
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this.kdf = kdf;
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this.mac = mac;
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this.macBuf = new byte[mac.GetMacSize()];
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this.cipher = cipher;
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}
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/**
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* Initialise the encryptor.
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*
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* @param forEncryption whether or not this is encryption/decryption.
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* @param privParam our private key parameters
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* @param pubParam the recipient's/sender's public key parameters
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* @param param encoding and derivation parameters.
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*/
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public void Init(
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bool forEncryption,
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ICipherParameters privParameters,
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ICipherParameters pubParameters,
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ICipherParameters iesParameters)
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{
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this.forEncryption = forEncryption;
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this.privParam = privParameters;
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this.pubParam = pubParameters;
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this.param = (IesParameters)iesParameters;
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}
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private byte[] DecryptBlock(
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byte[] in_enc,
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int inOff,
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int inLen,
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byte[] z)
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{
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byte[] M = null;
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KeyParameter macKey = null;
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KdfParameters kParam = new KdfParameters(z, param.GetDerivationV());
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int macKeySize = param.MacKeySize;
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kdf.Init(kParam);
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inLen -= mac.GetMacSize();
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if (cipher == null) // stream mode
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{
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byte[] Buffer = GenerateKdfBytes(kParam, inLen + (macKeySize / 8));
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M = new byte[inLen];
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for (int i = 0; i != inLen; i++)
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{
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M[i] = (byte)(in_enc[inOff + i] ^ Buffer[i]);
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}
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macKey = new KeyParameter(Buffer, inLen, (macKeySize / 8));
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}
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else
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{
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int cipherKeySize = ((IesWithCipherParameters)param).CipherKeySize;
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byte[] Buffer = GenerateKdfBytes(kParam, (cipherKeySize / 8) + (macKeySize / 8));
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cipher.Init(false, new KeyParameter(Buffer, 0, (cipherKeySize / 8)));
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M = cipher.DoFinal(in_enc, inOff, inLen);
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macKey = new KeyParameter(Buffer, (cipherKeySize / 8), (macKeySize / 8));
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}
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byte[] macIV = param.GetEncodingV();
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mac.Init(macKey);
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mac.BlockUpdate(in_enc, inOff, inLen);
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mac.BlockUpdate(macIV, 0, macIV.Length);
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mac.DoFinal(macBuf, 0);
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inOff += inLen;
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for (int t = 0; t < macBuf.Length; t++)
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{
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if (macBuf[t] != in_enc[inOff + t])
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{
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throw (new InvalidCipherTextException("IMac codes failed to equal."));
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}
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}
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return M;
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}
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private byte[] EncryptBlock(
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byte[] input,
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int inOff,
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int inLen,
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byte[] z)
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{
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byte[] C = null;
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KeyParameter macKey = null;
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KdfParameters kParam = new KdfParameters(z, param.GetDerivationV());
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int c_text_length = 0;
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int macKeySize = param.MacKeySize;
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if (cipher == null) // stream mode
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{
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byte[] Buffer = GenerateKdfBytes(kParam, inLen + (macKeySize / 8));
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C = new byte[inLen + mac.GetMacSize()];
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c_text_length = inLen;
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for (int i = 0; i != inLen; i++)
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{
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C[i] = (byte)(input[inOff + i] ^ Buffer[i]);
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}
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macKey = new KeyParameter(Buffer, inLen, (macKeySize / 8));
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}
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else
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{
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int cipherKeySize = ((IesWithCipherParameters)param).CipherKeySize;
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byte[] Buffer = GenerateKdfBytes(kParam, (cipherKeySize / 8) + (macKeySize / 8));
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cipher.Init(true, new KeyParameter(Buffer, 0, (cipherKeySize / 8)));
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c_text_length = cipher.GetOutputSize(inLen);
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byte[] tmp = new byte[c_text_length];
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int len = cipher.ProcessBytes(input, inOff, inLen, tmp, 0);
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len += cipher.DoFinal(tmp, len);
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C = new byte[len + mac.GetMacSize()];
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c_text_length = len;
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Array.Copy(tmp, 0, C, 0, len);
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macKey = new KeyParameter(Buffer, (cipherKeySize / 8), (macKeySize / 8));
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}
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byte[] macIV = param.GetEncodingV();
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mac.Init(macKey);
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mac.BlockUpdate(C, 0, c_text_length);
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mac.BlockUpdate(macIV, 0, macIV.Length);
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//
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// return the message and it's MAC
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//
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mac.DoFinal(C, c_text_length);
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return C;
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}
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private byte[] GenerateKdfBytes(
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KdfParameters kParam,
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int length)
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{
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byte[] buf = new byte[length];
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kdf.Init(kParam);
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kdf.GenerateBytes(buf, 0, buf.Length);
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return buf;
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}
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public byte[] ProcessBlock(
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byte[] input,
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int inOff,
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int inLen)
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{
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agree.Init(privParam);
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BigInteger z = agree.CalculateAgreement(pubParam);
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// TODO Check that this is right (...Unsigned? Check length?)
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byte[] zBytes = z.ToByteArray();
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return forEncryption
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? EncryptBlock(input, inOff, inLen, zBytes)
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: DecryptBlock(input, inOff, inLen, zBytes);
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}
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}
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}
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