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/*
-----------------------------------------------------------------------
Copyright (c) 2001 Dr Brian Gladman <brg@gladman.uk.net>, Worcester, UK
TERMS
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
This software is provided 'as is' with no guarantees of correctness or
fitness for purpose.
-----------------------------------------------------------------------
1. FUNCTION
The AES algorithm Rijndael implemented for block and key sizes of
128 bits (16 bytes) by Brian Gladman.
This is an implementation of the AES encryption algorithm (Rijndael)
designed by Joan Daemen and Vincent Rijmen.
2. THE CIPHER INTERFACE
byte (an unsigned 8-bit type)
word (an unsigned 32-bit type)
aes_ret: (a signed 16 bit type for function return values)
aes_good (value != 0, a good return)
aes_bad (value == 0, an error return)
enum aes_key: (encryption direction)
enc (set key for encryption)
dec (set key for decryption)
both (set key for both)
class or struct aes (structure for context)
C subroutine calls:
aes_ret set_blk(const word block_length, aes *cx) (variable block size)
aes_ret set_key(const byte key[], const word key_length,
const enum aes_key direction, aes *cx)
aes_ret encrypt(const byte input_blk[], byte output_blk[], const aes *cx)
aes_ret decrypt(const byte input_blk[], byte output_blk[], const aes *cx)
IMPORTANT NOTE: If you are using this C interface and your compiler does
not set the memory used for objects to zero before use, you will need to
ensure that cx.mode is set to zero before using the C subroutine calls.
The block length inputs to set_block and set_key are in numbers of
BYTES, not bits. The calls to subroutines must be made in the above
order but multiple calls can be made without repeating earlier calls
if their parameters have not changed. If the cipher block length is
variable but set_blk has not been called before cipher operations a
value of 16 is assumed (that is, the AES block size). In contrast to
earlier versions the block and key length parameters are now checked
for correctness and the encryption and decryption routines check to
ensure that an appropriate key has been set before they are called.
*/
#ifndef _AES_H
#define _AES_H
/* The only supported block size for the benchmark is 16 */
#define BLOCK_SIZE 16
/*
The number of key schedule words for different block and key lengths
(allowing for the method of computation which requires the length to
be a multiple of the key length):
Key Schedule key length (bytes)
Length 16 20 24 28 32
---------------------
block 16 | 44 60 54 56 64
length 20 | 60 60 66 70 80
(bytes) 24 | 80 80 78 84 96
28 | 100 100 102 98 112
32 | 120 120 120 126 120
Rcon Table key length (bytes)
Length 16 20 24 28 32
---------------------
block 16 | 10 9 8 7 7
length 20 | 14 11 10 9 9
(bytes) 24 | 19 15 12 11 11
28 | 24 19 16 13 13
32 | 29 23 19 17 14
The following values assume that the key length will be variable and may
be of maximum length (32 bytes).
Nk = number_of_key_bytes / 4
Nc = number_of_columns_in_state / 4
Nr = number of encryption/decryption rounds
Rc = number of elements in rcon table
Ks = number of 32-bit words in key schedule
*/
#define Nr(Nk,Nc) ((Nk > Nc ? Nk : Nc) + 6)
#define Rc(Nk,Nc) ((Nb * (Nr(Nk,Nc) + 1) - 1) / Nk)
#define Ks(Nk,Nc) (Nk * (Rc(Nk,Nc) + 1))
#define RC_LENGTH 5 * BLOCK_SIZE / 4 - (BLOCK_SIZE == 16 ? 10 : 11)
#define KS_LENGTH 4 * BLOCK_SIZE
/* End of configuration options, but see also aes.c */
typedef unsigned char byte; /* must be an 8-bit storage unit */
typedef unsigned long word; /* must be a 32-bit storage unit */
typedef short aes_ret; /* function return value */
#define aes_bad 0
#define aes_good 1
/*
upr(x,n): rotates bytes within words by n positions, moving bytes
to higher index positions with wrap around into low positions
ups(x,n): moves bytes by n positions to higher index positions in
words but without wrap around
bval(x,n): extracts a byte from a word
*/
#define upr(x,n) (((x) << 8 * (n)) | ((x) >> (32 - 8 * (n))))
#define ups(x,n) ((x) << 8 * (n))
#define bval(x,n) ((byte)((x) >> 8 * (n)))
#define byte_swap(x) (upr(x,1) & 0x00ff00ff | upr(x,3) & 0xff00ff00)
#define bytes2word(b0, b1, b2, b3) ((word)(b3) << 24 | (word)(b2) << 16 | \
(word)(b1) << 8 | (b0))
#define word_in(x) *(word*)(x)
#define word_out(x,v) *(word*)(x) = (v)
enum aes_const { Nrow = 4, /* the number of rows in the cipher state */
Mcol = 8, /* maximum number of columns in the state */
Ncol = BLOCK_SIZE / 4,
Shr0 = 0, /* the cyclic shift values for rows 0, 1, 2 & 3 */
Shr1 = 1,
Shr2 = BLOCK_SIZE == 32 ? 3 : 2,
Shr3 = BLOCK_SIZE == 32 ? 4 : 3
};
enum aes_key { enc = 1, /* set if encryption is needed */
dec = 2, /* set if decryption is needed */
both = 3 /* set if both are needed */
};
struct aes {
word Nkey; /* the number of words in the key input block */
word Nrnd; /* the number of cipher rounds */
word e_key[KS_LENGTH]; /* the encryption key schedule */
word d_key[KS_LENGTH]; /* the decryption key schedule */
byte mode; /* encrypt, decrypt or both */
};
aes_ret rijndael_dec_set_key( byte key[], const word n_bytes,
const enum aes_key f, struct aes *cx );
aes_ret rijndael_dec_decrypt( const byte in_blk[], byte out_blk[],
const struct aes *cx );
#endif
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