code: func decrypt(block cipher.Block, dst, src, buf []byte) {
  	switch block.BlockSize() {
  	case 8:
  		decrypt8(block, dst, src, buf)
  	case 16:
  		decrypt16(block, dst, src, buf)
  	default:
  		decryptVariant(block, dst, src, buf)
  	}
  }
docs: // decryption