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ruanhaishen
Tiny AES C
Commits
be76dd85
Commit
be76dd85
authored
May 29, 2014
by
kokke
Browse files
Create aes.c
parent
2832a465
Changes
1
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aes.c
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be76dd85
/*
This is the implementation of the AES128 algorithm, specifically ECB mode.
The implementation is verified against the test vectors in:
National Institute of Standards and Technology Special Publication 800-38A 2001 ED
ECB-AES128
----------
plain-text:
6bc1bee22e409f96e93d7e117393172a
ae2d8a571e03ac9c9eb76fac45af8e51
30c81c46a35ce411e5fbc1191a0a52ef
f69f2445df4f9b17ad2b417be66c3710
key:
2b7e151628aed2a6abf7158809cf4f3c
resulting cipher
50fe67cc996d32b6da0937e99bafec60
d9a4dada0892239f6b8b3d7680e15674
a78819583f0308e7a6bf36b1386abf23
c6d3416d29165c6fcb8e51a227ba994e
Use aes_encrypt_string() to encrypt or decrypt a string
NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0)
You should pad the end of the string with zeros if this is not the case.
*/
#ifndef _AES_C_
#define _AES_C_
/*****************************************************************************/
/* Includes: */
/*****************************************************************************/
#include <string.h>
#include <stdint.h>
#include "aes.h"
/*****************************************************************************/
/* Defines: */
/*****************************************************************************/
// The number of columns comprising a state in AES. This is a constant in AES. Value=4
#define Nb 4
// The number of 32 bit words in a key.
#define Nk 4
// Key length in bytes [128 bit]
#define keyln 16
// The number of rounds in AES Cipher.
#define Nr 10
/*****************************************************************************/
/* Private variables: */
/*****************************************************************************/
// in - pointer to the CipherText to be decrypted.
// out - pointer to buffer to hold output of the decryption.
// state - array holding the intermediate results during decryption.
static
uint8_t
*
in
,
*
out
,
state
[
4
][
4
];
// The array that stores the round keys.
static
uint8_t
RoundKey
[
176
];
// The Key input to the AES Program
static
uint8_t
*
Key
;
// Marked const so it can be placed in read-only storage instead of RAM
// The numbers below can be computed dynamically trading ROM for RAM -
// This can be useful in (embedded) bootloader applications, where ROM is often limited.
static
const
uint8_t
sbox
[
256
]
=
{
//0 1 2 3 4 5 6 7 8 9 A B C D E F
0x63
,
0x7c
,
0x77
,
0x7b
,
0xf2
,
0x6b
,
0x6f
,
0xc5
,
0x30
,
0x01
,
0x67
,
0x2b
,
0xfe
,
0xd7
,
0xab
,
0x76
,
0xca
,
0x82
,
0xc9
,
0x7d
,
0xfa
,
0x59
,
0x47
,
0xf0
,
0xad
,
0xd4
,
0xa2
,
0xaf
,
0x9c
,
0xa4
,
0x72
,
0xc0
,
0xb7
,
0xfd
,
0x93
,
0x26
,
0x36
,
0x3f
,
0xf7
,
0xcc
,
0x34
,
0xa5
,
0xe5
,
0xf1
,
0x71
,
0xd8
,
0x31
,
0x15
,
0x04
,
0xc7
,
0x23
,
0xc3
,
0x18
,
0x96
,
0x05
,
0x9a
,
0x07
,
0x12
,
0x80
,
0xe2
,
0xeb
,
0x27
,
0xb2
,
0x75
,
0x09
,
0x83
,
0x2c
,
0x1a
,
0x1b
,
0x6e
,
0x5a
,
0xa0
,
0x52
,
0x3b
,
0xd6
,
0xb3
,
0x29
,
0xe3
,
0x2f
,
0x84
,
0x53
,
0xd1
,
0x00
,
0xed
,
0x20
,
0xfc
,
0xb1
,
0x5b
,
0x6a
,
0xcb
,
0xbe
,
0x39
,
0x4a
,
0x4c
,
0x58
,
0xcf
,
0xd0
,
0xef
,
0xaa
,
0xfb
,
0x43
,
0x4d
,
0x33
,
0x85
,
0x45
,
0xf9
,
0x02
,
0x7f
,
0x50
,
0x3c
,
0x9f
,
0xa8
,
0x51
,
0xa3
,
0x40
,
0x8f
,
0x92
,
0x9d
,
0x38
,
0xf5
,
0xbc
,
0xb6
,
0xda
,
0x21
,
0x10
,
0xff
,
0xf3
,
0xd2
,
0xcd
,
0x0c
,
0x13
,
0xec
,
0x5f
,
0x97
,
0x44
,
0x17
,
0xc4
,
0xa7
,
0x7e
,
0x3d
,
0x64
,
0x5d
,
0x19
,
0x73
,
0x60
,
0x81
,
0x4f
,
0xdc
,
0x22
,
0x2a
,
0x90
,
0x88
,
0x46
,
0xee
,
0xb8
,
0x14
,
0xde
,
0x5e
,
0x0b
,
0xdb
,
0xe0
,
0x32
,
0x3a
,
0x0a
,
0x49
,
0x06
,
0x24
,
0x5c
,
0xc2
,
0xd3
,
0xac
,
0x62
,
0x91
,
0x95
,
0xe4
,
0x79
,
0xe7
,
0xc8
,
0x37
,
0x6d
,
0x8d
,
0xd5
,
0x4e
,
0xa9
,
0x6c
,
0x56
,
0xf4
,
0xea
,
0x65
,
0x7a
,
0xae
,
0x08
,
0xba
,
0x78
,
0x25
,
0x2e
,
0x1c
,
0xa6
,
0xb4
,
0xc6
,
0xe8
,
0xdd
,
0x74
,
0x1f
,
0x4b
,
0xbd
,
0x8b
,
0x8a
,
0x70
,
0x3e
,
0xb5
,
0x66
,
0x48
,
0x03
,
0xf6
,
0x0e
,
0x61
,
0x35
,
0x57
,
0xb9
,
0x86
,
0xc1
,
0x1d
,
0x9e
,
0xe1
,
0xf8
,
0x98
,
0x11
,
0x69
,
0xd9
,
0x8e
,
0x94
,
0x9b
,
0x1e
,
0x87
,
0xe9
,
0xce
,
0x55
,
0x28
,
0xdf
,
0x8c
,
0xa1
,
0x89
,
0x0d
,
0xbf
,
0xe6
,
0x42
,
0x68
,
0x41
,
0x99
,
0x2d
,
0x0f
,
0xb0
,
0x54
,
0xbb
,
0x16
};
// The round constant word array, Rcon[i], contains the values given by
// x to th e power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
// Note that i starts at 1, not 0).
static
const
uint8_t
Rcon
[
255
]
=
{
0x8d
,
0x01
,
0x02
,
0x04
,
0x08
,
0x10
,
0x20
,
0x40
,
0x80
,
0x1b
,
0x36
,
0x6c
,
0xd8
,
0xab
,
0x4d
,
0x9a
,
0x2f
,
0x5e
,
0xbc
,
0x63
,
0xc6
,
0x97
,
0x35
,
0x6a
,
0xd4
,
0xb3
,
0x7d
,
0xfa
,
0xef
,
0xc5
,
0x91
,
0x39
,
0x72
,
0xe4
,
0xd3
,
0xbd
,
0x61
,
0xc2
,
0x9f
,
0x25
,
0x4a
,
0x94
,
0x33
,
0x66
,
0xcc
,
0x83
,
0x1d
,
0x3a
,
0x74
,
0xe8
,
0xcb
,
0x8d
,
0x01
,
0x02
,
0x04
,
0x08
,
0x10
,
0x20
,
0x40
,
0x80
,
0x1b
,
0x36
,
0x6c
,
0xd8
,
0xab
,
0x4d
,
0x9a
,
0x2f
,
0x5e
,
0xbc
,
0x63
,
0xc6
,
0x97
,
0x35
,
0x6a
,
0xd4
,
0xb3
,
0x7d
,
0xfa
,
0xef
,
0xc5
,
0x91
,
0x39
,
0x72
,
0xe4
,
0xd3
,
0xbd
,
0x61
,
0xc2
,
0x9f
,
0x25
,
0x4a
,
0x94
,
0x33
,
0x66
,
0xcc
,
0x83
,
0x1d
,
0x3a
,
0x74
,
0xe8
,
0xcb
,
0x8d
,
0x01
,
0x02
,
0x04
,
0x08
,
0x10
,
0x20
,
0x40
,
0x80
,
0x1b
,
0x36
,
0x6c
,
0xd8
,
0xab
,
0x4d
,
0x9a
,
0x2f
,
0x5e
,
0xbc
,
0x63
,
0xc6
,
0x97
,
0x35
,
0x6a
,
0xd4
,
0xb3
,
0x7d
,
0xfa
,
0xef
,
0xc5
,
0x91
,
0x39
,
0x72
,
0xe4
,
0xd3
,
0xbd
,
0x61
,
0xc2
,
0x9f
,
0x25
,
0x4a
,
0x94
,
0x33
,
0x66
,
0xcc
,
0x83
,
0x1d
,
0x3a
,
0x74
,
0xe8
,
0xcb
,
0x8d
,
0x01
,
0x02
,
0x04
,
0x08
,
0x10
,
0x20
,
0x40
,
0x80
,
0x1b
,
0x36
,
0x6c
,
0xd8
,
0xab
,
0x4d
,
0x9a
,
0x2f
,
0x5e
,
0xbc
,
0x63
,
0xc6
,
0x97
,
0x35
,
0x6a
,
0xd4
,
0xb3
,
0x7d
,
0xfa
,
0xef
,
0xc5
,
0x91
,
0x39
,
0x72
,
0xe4
,
0xd3
,
0xbd
,
0x61
,
0xc2
,
0x9f
,
0x25
,
0x4a
,
0x94
,
0x33
,
0x66
,
0xcc
,
0x83
,
0x1d
,
0x3a
,
0x74
,
0xe8
,
0xcb
,
0x8d
,
0x01
,
0x02
,
0x04
,
0x08
,
0x10
,
0x20
,
0x40
,
0x80
,
0x1b
,
0x36
,
0x6c
,
0xd8
,
0xab
,
0x4d
,
0x9a
,
0x2f
,
0x5e
,
0xbc
,
0x63
,
0xc6
,
0x97
,
0x35
,
0x6a
,
0xd4
,
0xb3
,
0x7d
,
0xfa
,
0xef
,
0xc5
,
0x91
,
0x39
,
0x72
,
0xe4
,
0xd3
,
0xbd
,
0x61
,
0xc2
,
0x9f
,
0x25
,
0x4a
,
0x94
,
0x33
,
0x66
,
0xcc
,
0x83
,
0x1d
,
0x3a
,
0x74
,
0xe8
,
0xcb
};
/*****************************************************************************/
/* Private functions: */
/*****************************************************************************/
static
uint8_t
getSBoxValue
(
uint8_t
num
)
{
return
sbox
[
num
];
}
// This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states.
static
void
KeyExpansion
()
{
uint8_t
i
,
j
,
k
;
uint8_t
tempa
[
4
];
// used for the column/row operations
// The first round key is the key itself.
for
(
i
=
0
;
i
<
Nk
;
++
i
)
{
RoundKey
[
i
*
4
]
=
Key
[
i
*
4
];
RoundKey
[(
i
*
4
)
+
1
]
=
Key
[(
i
*
4
)
+
1
];
RoundKey
[(
i
*
4
)
+
2
]
=
Key
[(
i
*
4
)
+
2
];
RoundKey
[(
i
*
4
)
+
3
]
=
Key
[(
i
*
4
)
+
3
];
}
// All other round keys are found from the previous round keys.
for
(;
(
i
<
(
Nb
*
Nr
)
+
1
);
++
i
)
{
for
(
j
=
0
;
j
<
4
;
++
j
)
{
tempa
[
j
]
=
RoundKey
[(
i
-
1
)
*
4
+
j
];
}
if
(
i
%
Nk
==
0
)
{
// This function rotates the 4 bytes in a word to the left once.
// [a0,a1,a2,a3] becomes [a1,a2,a3,a0]
// Function RotWord()
{
k
=
tempa
[
0
];
tempa
[
0
]
=
tempa
[
1
];
tempa
[
1
]
=
tempa
[
2
];
tempa
[
2
]
=
tempa
[
3
];
tempa
[
3
]
=
k
;
}
// SubWord() is a function that takes a four-byte input word and
// applies the S-box to each of the four bytes to produce an output word.
// Function Subword()
{
tempa
[
0
]
=
getSBoxValue
(
tempa
[
0
]);
tempa
[
1
]
=
getSBoxValue
(
tempa
[
1
]);
tempa
[
2
]
=
getSBoxValue
(
tempa
[
2
]);
tempa
[
3
]
=
getSBoxValue
(
tempa
[
3
]);
}
tempa
[
0
]
=
tempa
[
0
]
^
Rcon
[
i
/
Nk
];
}
else
if
(
Nk
>
6
&&
i
%
Nk
==
4
)
{
// Function Subword()
{
tempa
[
0
]
=
getSBoxValue
(
tempa
[
0
]);
tempa
[
1
]
=
getSBoxValue
(
tempa
[
1
]);
tempa
[
2
]
=
getSBoxValue
(
tempa
[
2
]);
tempa
[
3
]
=
getSBoxValue
(
tempa
[
3
]);
}
}
RoundKey
[
i
*
4
]
=
RoundKey
[
i
-
Nk
*
4
]
^
tempa
[
0
];
RoundKey
[(
i
*
4
)
+
1
]
=
RoundKey
[(
i
-
Nk
)
*
(
4
+
1
)]
^
tempa
[
1
];
RoundKey
[(
i
*
4
)
+
2
]
=
RoundKey
[(
i
-
Nk
)
*
(
4
+
2
)]
^
tempa
[
2
];
RoundKey
[(
i
*
4
)
+
3
]
=
RoundKey
[(
i
-
Nk
)
*
(
4
+
3
)]
^
tempa
[
3
];
}
}
// This function adds the round key to state.
// The round key is added to the state by an XOR function.
static
void
AddRoundKey
(
uint8_t
round
)
{
uint8_t
i
,
j
;
for
(
i
=
0
;
i
<
4
;
i
++
)
{
for
(
j
=
0
;
j
<
4
;
++
j
)
{
state
[
j
][
i
]
^=
RoundKey
[
round
*
Nb
*
4
+
i
*
Nb
+
j
];
}
}
}
// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static
void
SubBytes
()
{
uint8_t
i
,
j
;
for
(
i
=
0
;
i
<
4
;
++
i
)
{
for
(
j
=
0
;
j
<
4
;
++
j
)
{
state
[
i
][
j
]
=
getSBoxValue
(
state
[
i
][
j
]);
}
}
}
// The ShiftRows() function shifts the rows in the state to the left.
// Each row is shifted with different offset.
// Offset = Row number. So the first row is not shifted.
static
void
ShiftRows
()
{
uint8_t
temp
;
// Rotate first row 1 columns to left
temp
=
state
[
1
][
0
];
state
[
1
][
0
]
=
state
[
1
][
1
];
state
[
1
][
1
]
=
state
[
1
][
2
];
state
[
1
][
2
]
=
state
[
1
][
3
];
state
[
1
][
3
]
=
temp
;
// Rotate second row 2 columns to left
temp
=
state
[
2
][
0
];
state
[
2
][
0
]
=
state
[
2
][
2
];
state
[
2
][
2
]
=
temp
;
temp
=
state
[
2
][
1
];
state
[
2
][
1
]
=
state
[
2
][
3
];
state
[
2
][
3
]
=
temp
;
// Rotate third row 3 columns to left
temp
=
state
[
3
][
0
];
state
[
3
][
0
]
=
state
[
3
][
3
];
state
[
3
][
3
]
=
state
[
3
][
2
];
state
[
3
][
2
]
=
state
[
3
][
1
];
state
[
3
][
1
]
=
temp
;
}
static
uint8_t
xtime
(
uint8_t
x
)
{
return
((
x
<<
1
)
^
(((
x
>>
7
)
&
1
)
*
0x1b
));
}
// MixColumns function mixes the columns of the state matrix
static
void
MixColumns
()
{
uint8_t
i
;
uint8_t
Tmp
,
Tm
,
t
;
for
(
i
=
0
;
i
<
4
;
++
i
)
{
t
=
state
[
0
][
i
];
Tmp
=
state
[
0
][
i
]
^
state
[
1
][
i
]
^
state
[
2
][
i
]
^
state
[
3
][
i
]
;
Tm
=
state
[
0
][
i
]
^
state
[
1
][
i
]
;
Tm
=
xtime
(
Tm
);
state
[
0
][
i
]
^=
Tm
^
Tmp
;
Tm
=
state
[
1
][
i
]
^
state
[
2
][
i
]
;
Tm
=
xtime
(
Tm
);
state
[
1
][
i
]
^=
Tm
^
Tmp
;
Tm
=
state
[
2
][
i
]
^
state
[
3
][
i
]
;
Tm
=
xtime
(
Tm
);
state
[
2
][
i
]
^=
Tm
^
Tmp
;
Tm
=
state
[
3
][
i
]
^
t
;
Tm
=
xtime
(
Tm
);
state
[
3
][
i
]
^=
Tm
^
Tmp
;
}
}
// Cipher is the main function that encrypts the PlainText.
static
void
Cipher
()
{
uint8_t
i
,
j
,
round
=
0
;
//Copy the input PlainText to state array.
for
(
i
=
0
;
i
<
4
;
++
i
)
{
for
(
j
=
0
;
j
<
4
;
++
j
)
{
state
[
j
][
i
]
=
in
[(
i
*
4
)
+
j
];
}
}
// Add the First round key to the state before starting the rounds.
AddRoundKey
(
0
);
// There will be Nr rounds.
// The first Nr-1 rounds are identical.
// These Nr-1 rounds are executed in the loop below.
for
(
round
=
1
;
round
<
Nr
;
++
round
)
{
SubBytes
();
ShiftRows
();
MixColumns
();
AddRoundKey
(
round
);
}
// The last round is given below.
// The MixColumns function is not here in the last round.
SubBytes
();
ShiftRows
();
AddRoundKey
(
Nr
);
// The encryption process is over.
// Copy the state array to output array.
for
(
i
=
0
;
i
<
4
;
++
i
)
{
for
(
j
=
0
;
j
<
4
;
++
j
)
{
out
[(
i
*
4
)
+
j
]
=
state
[
j
][
i
];
}
}
}
/*****************************************************************************/
/* Public functions: */
/*****************************************************************************/
void
AES128_ECB
(
uint8_t
*
input
,
uint8_t
*
key
,
uint8_t
*
output
)
{
// Copy the Key and CipherText
Key
=
key
;
in
=
input
;
out
=
output
;
// The KeyExpansion routine must be called before encryption.
KeyExpansion
();
// The next function call encrypts the PlainText with the Key using AES algorithm.
Cipher
();
}
#endif //_AES_C_
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