/// <summary>
/// 以CBC模式加密明文二进制数组
/// </summary>
/// <param name="iv">输出本次加密使用的初始向量。算法会使用Randomizer成员初始化这个数组</param>
/// <param name="plain">明文</param>
/// <param name="key">密钥</param>
/// <returns>加密后的数据块（不包括初始向量）</returns>
public static byte[] EncryptCBC(this IBlockEncryption enc, out byte[] iv, byte[] plain, byte[] key)
{
int BlockSize = enc.BlockSize;
byte[] p = enc.Padder(plain);
iv = new byte[BlockSize];
enc.Randomizer(iv); Debug.Print(iv.ToHexString());
int block_count = p.Length / BlockSize;
for (int i = 0; i < block_count; i++)
{
int this_block = i * BlockSize;
int pre_block = this_block - BlockSize;
if (i == 0)
{
XorBlock(enc, iv, 0, p, this_block);
}
else
{
XorBlock(enc, p, pre_block, p, this_block);
}
enc.Encryptor(p, this_block, key);
}
return(p);
}
/// <summary>
/// 以EBC模式解密密文二进制数组
/// </summary>
/// <param name="cipher">密文</param>
/// <param name="key">密钥</param>
/// <returns>明文</returns>
public static byte[] DecryptEBC(this IBlockEncryption enc, byte[] cipher, byte[] key)
{
int BlockSize = enc.BlockSize;
byte[] c = (byte[])cipher.Clone();
int block_count = c.Length / BlockSize;
for (int i = block_count - 1; i > 0; i--)
{
enc.Decryptor(c, i * BlockSize, key);
}
return(c);
}
/// <summary>
/// 以EBC模式加密明文二进制数组
/// </summary>
/// <param name="plain">明文</param>
/// <param name="key">密钥</param>
/// <returns>密文</returns>
public static byte[] EncryptEBC(this IBlockEncryption enc, byte[] plain, byte[] key)
{
int BlockSize = enc.BlockSize;
byte[] p = enc.Padder(plain);
int block_count = p.Length / BlockSize;
for (int i = 0; i < block_count; i++)
{
enc.Encryptor(p, i * BlockSize, key);
}
return(p);
}
private static void XorBlock(IBlockEncryption enc, byte[] left, int left_index, byte[] right, int right_index)
{
int BlockSize = enc.BlockSize;
if (left_index + BlockSize > left.Length)
{
throw new Exception($"异或式的左值长度不足，索引[{left_index}]之后的数据长度不足{BlockSize}");
}
else if (right_index + BlockSize > right.Length)
{
throw new Exception($"异或式的右值长度不足，索引[{right_index}]之后的数据长度不足{BlockSize}");
}
for (int i = 0; i < enc.BlockSize; i++)
{
right[right_index + i] = (byte)(left[left_index + i] ^ right[right_index + i]);
}
}
/// <summary>
/// 以CBC模式解密密文二进制数组
/// </summary>
/// <param name="iv">初始向量。用于解密第一个数据块</param>
/// <param name="cipher">密文</param>
/// <param name="key">密钥</param>
/// <returns>解密后的数据块（不包括初始向量）</returns>
public static byte[] DecryptCBC(this IBlockEncryption enc, byte[] iv, byte[] cipher, byte[] key)
{
int BlockSize = enc.BlockSize;
byte[] c = (byte[])cipher.Clone();
int block_count = c.Length / BlockSize;
for (int i = block_count - 1; i >= 0; i--)
{
int this_block = i * BlockSize;
int pre_block = this_block - BlockSize;
enc.Decryptor(c, this_block, key);
if (i == 0)
{
XorBlock(enc, iv, 0, c, this_block);
}
else
{
XorBlock(enc, c, pre_block, c, this_block);
}
}
return(c);
}
