crypto: add a crypto.des module (#13065)

vlib/crypto/cipher/cipher.v

@@ -0,0 +1,55 @@
+// The source code refers to the go standard library, which will be combined with AES in the future.
+
+module cipher
+
+// A Block represents an implementation of block cipher
+// using a given key. It provides the capability to encrypt
+// or decrypt individual blocks. The mode implementations
+// extend that capability to streams of blocks.
+interface Block {
+	block_size int // block_size returns the cipher's block size.
+	encrypt(mut dst []byte, src []byte) // Encrypt encrypts the first block in src into dst.
+	// Dst and src must overlap entirely or not at all.
+	decrypt(mut dst []byte, src []byte) // Decrypt decrypts the first block in src into dst.
+	// Dst and src must overlap entirely or not at all.
+}
+
+// A Stream represents a stream cipher.
+interface Stream {
+	// xor_key_stream XORs each byte in the given slice with a byte from the
+	// cipher's key stream. Dst and src must overlap entirely or not at all.
+	//
+	// If len(dst) < len(src), xor_key_stream should panic. It is acceptable
+	// to pass a dst bigger than src, and in that case, xor_key_stream will
+	// only update dst[:len(src)] and will not touch the rest of dst.
+	//
+	// Multiple calls to xor_key_stream behave as if the concatenation of
+	// the src buffers was passed in a single run. That is, Stream
+	// maintains state and does not reset at each xor_key_stream call.
+	xor_key_stream(mut dst []byte, src []byte)
+}
+
+// A BlockMode represents a block cipher running in a block-based mode (CBC,
+// ECB etc).
+interface BlockMode {
+	block_size int // block_size returns the mode's block size.
+	crypt_blocks(mut dst []byte, src []byte) // crypt_blocks encrypts or decrypts a number of blocks. The length of
+	// src must be a multiple of the block size. Dst and src must overlap
+	// entirely or not at all.
+	//
+	// If len(dst) < len(src), crypt_blocks should panic. It is acceptable
+	// to pass a dst bigger than src, and in that case, crypt_blocks will
+	// only update dst[:len(src)] and will not touch the rest of dst.
+	//
+	// Multiple calls to crypt_blocks behave as if the concatenation of
+	// the src buffers was passed in a single run. That is, BlockMode
+	// maintains state and does not reset at each crypt_blocks call.
+}
+
+// Utility routines
+
+// fn dup(p []byte) []byte {
+// 	q := make([]byte, p.len)
+// 	copy(q, p)
+// 	return q
+// }