Org.BouncyCastle.Crypto.Encodings.Pkcs1Encoding.DecodeBlock C# (CSharp) Method

		private byte[] DecodeBlock(
			byte[]	input,
			int		inOff,
			int		inLen)
		{
			byte[] block = engine.ProcessBlock(input, inOff, inLen);

			if (block.Length < GetOutputBlockSize())
			{
				throw new InvalidCipherTextException("block truncated");
			}

			byte type = block[0];

			if (type != 1 && type != 2)
			{
				throw new InvalidCipherTextException("unknown block type");
			}

			if (useStrictLength && block.Length != engine.GetOutputBlockSize())
			{
				throw new InvalidCipherTextException("block incorrect size");
			}

			//
			// find and extract the message block.
			//
			int start;
			for (start = 1; start != block.Length; start++)
			{
				byte pad = block[start];

				if (pad == 0)
				{
					break;
				}

				if (type == 1 && pad != (byte)0xff)
				{
					throw new InvalidCipherTextException("block padding incorrect");
				}
			}

			start++;           // data should start at the next byte

			if (start >= block.Length || start < HeaderLength)
			{
				throw new InvalidCipherTextException("no data in block");
			}

			byte[] result = new byte[block.Length - start];

			Array.Copy(block, start, result, 0, result.Length);

			return result;
		}
	}