// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package cipher implements standard block cipher modes that can be wrapped
// around low-level block cipher implementations.
// See https://csrc.nist.gov/groups/ST/toolkit/BCM/current_modes.html
// and NIST Special Publication 800-38A.
package 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.
type Block interface {
// BlockSize returns the cipher's block size.
BlockSize() int
// Encrypt encrypts the first block in src into dst.
// Dst and src must overlap entirely or not at all.
Encrypt(dst, src []byte)
// Decrypt decrypts the first block in src into dst.
// Dst and src must overlap entirely or not at all.
Decrypt(dst, src []byte)
}
// A Stream represents a stream cipher.
type Stream interface {
// XORKeyStream 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), XORKeyStream should panic. It is acceptable
// to pass a dst bigger than src, and in that case, XORKeyStream will
// only update dst[:len(src)] and will not touch the rest of dst.
//
// Multiple calls to XORKeyStream 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 XORKeyStream call.
XORKeyStream(dst, src []byte)
}
// A BlockMode represents a block cipher running in a block-based mode (CBC,
// ECB etc).
type BlockMode interface {
// BlockSize returns the mode's block size.
BlockSize() int
// CryptBlocks 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), CryptBlocks should panic. It is acceptable
// to pass a dst bigger than src, and in that case, CryptBlocks will
// only update dst[:len(src)] and will not touch the rest of dst.
//
// Multiple calls to CryptBlocks 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 CryptBlocks call.
CryptBlocks(dst, src []byte)
}
// AEAD is a cipher mode providing authenticated encryption with associated
// data. For a description of the methodology, see
// https://en.wikipedia.org/wiki/Authenticated_encryption.
type AEAD interface {
// NonceSize returns the size of the nonce that must be passed to Seal
// and Open.
NonceSize() int
// Overhead returns the maximum difference between the lengths of a
// plaintext and its ciphertext.
Overhead() int
// Seal encrypts and authenticates plaintext, authenticates the
// additional data and appends the result to dst, returning the updated
// slice. The nonce must be NonceSize() bytes long and unique for all
// time, for a given key.
//
// To reuse plaintext's storage for the encrypted output, use plaintext[:0]
// as dst. Otherwise, the remaining capacity of dst must not overlap plaintext.
// dst and additionalData may not overlap.
Seal(dst, nonce, plaintext, additionalData []byte) []byte
// Open decrypts and authenticates ciphertext, authenticates the
// additional data and, if successful, appends the resulting plaintext
// to dst, returning the updated slice. The nonce must be NonceSize()
// bytes long and both it and the additional data must match the
// value passed to Seal.
//
// To reuse ciphertext's storage for the decrypted output, use ciphertext[:0]
// as dst. Otherwise, the remaining capacity of dst must not overlap ciphertext.
// dst and additionalData may not overlap.
//
// Even if the function fails, the contents of dst, up to its capacity,
// may be overwritten.
Open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error)
}
