plan9fox/sys/man/2/aes

.TH AES 2
.SH NAME
setupAESstate, \
aesCBCencrypt, \
aesCBCdecrypt, \
aesCFBencrypt, \
aesCFBdecrypt, \
aesOFBencrypt, \
aes_xts_encrypt, aes_xts_decrypt, \
setupAESGCMstate, \
aesgcm_setiv, aesgcm_encrypt, aesgcm_decrypt \
- advanced encryption standard (rijndael)
.SH SYNOPSIS
.B #include <u.h>
.br
.B #include <libc.h>
.br
.B #include <mp.h>
.br
.B #include <libsec.h>
.PP
.in +0.5i
.ti -0.5i
.PP
.B
void	aes_encrypt(ulong rk[], int Nr, uchar pt[16], uchar ct[16])
.PP
.B
void	aes_decrypt(ulong rk[], int Nr, uchar ct[16], uchar pt[16])
.PP
.B
void	setupAESstate(AESstate *s, uchar key[], int nkey, uchar *ivec)
.PP
.B
void	aesCBCencrypt(uchar *p, int len, AESstate *s)
.PP
.B
void	aesCBCdecrypt(uchar *p, int len, AESstate *s)
.PP
.B
void	aesCFBencrypt(uchar *p, int len, AESstate *s)
.PP
.B
void	aesCFBdecrypt(uchar *p, int len, AESstate *s)
.PP
.B
void	aesOFBencrypt(uchar *p, int len, AESstate *s)
.PP
.B
void	aes_xts_encrypt(AESstate *tweak, AESstate *ecb, uvlong sectorNumber, uchar *input, uchar *output, ulong len)
.PP
.B
void	aes_xts_decrypt(AESstate *tweak, AESstate *ecb, uvlong sectorNumber, uchar *input, uchar *output, ulong len)
.PP
.B
void	setupAESGCMstate(AESGCMstate *s, uchar *key, int keylen, uchar *iv, int ivlen)
.PP
.B
void	aesgcm_setiv(AESGCMstate *s, uchar *iv, int ivlen)
.PP
.B
void	aesgcm_encrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], AESGCMstate *s)
.PP
.B
int	aesgcm_decrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], AESGCMstate *s)
.SH DESCRIPTION
AES (a.k.a. Rijndael) has replaced DES as the preferred
block cipher.
.I Aes_encrypt
and
.I aes_decrypt
are the block ciphers, corresponding to
.IR des (2)'s
.IR block_cipher .
.I AesCBCencrypt
and
.I aesCBCdecrypt
implement cipher-block-chaining encryption.
.IR AesCFBencrypt ,
.I aesCFBdecrypt
and
.I aesOFBencrypt
implement cipher-feedback- and output-feedback-mode
stream cipher encryption.
.I Aes_xts_encrypt
and
.I aes_xts_decrypt
implement the XTS-AES tweakable block cipher, per IEEE 1619-2017 (see bugs below).
.IR SetupAESstate
is used to initialize the state of the above encryption modes.
The expanded roundkey parameters
.I rk
and
.I Nr
of
.I aes_encrypt
and
.I aes_decrypt
are returned in
.I AESstate.ekey
and
.I AESstate.dkey
with the corresponding number of rounds in
.IR AESstate.rounds .
.IR SetupAESGCMstate ,
.IR aesgcm_setiv ,
.I aesgcm_encrypt
and
.I aesgcm_decrypt
implement Galois/Counter Mode (GCM) authenticated encryption with associated data (AEAD).
Before encryption or decryption, a new initialization vector (nonce) has to be set with
.I aesgcm_setiv
or by calling
.I setupAESGCMstate
with non-zero
.I iv
and
.I ivlen
arguments.
Aesgcm_decrypt returns zero when authentication and decryption where successfull and
non-zero otherwise.
All ciphering is performed in place.
The byte keysize
.I nkey
should be 16, 24, or 32.
The initialization vector
.I ivec
of
.I AESbsize
bytes should be random enough to be unlikely to be reused
but does not need to be
cryptographically strongly unpredictable.
.SH SOURCE
.B /sys/src/libsec
.SH SEE ALSO
.I aescbc
in
.IR secstore (1),
.IR mp (2),
.IR blowfish (2),
.IR des (2),
.IR dsa (2),
.IR elgamal (2),
.IR rc4 (2),
.IR rsa (2),
.IR sechash (2),
.IR prime (2),
.IR rand (2)
.br
.B http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
.SH BUGS
Because of the way that non-multiple-of-16 buffers are handled,
.I aesCBCdecrypt
must be fed buffers of the same size as the
.I aesCBCencrypt
calls that encrypted it.
.PP
The functions
.I aes_xts_encrypt
an
.I aes_xts_decrypt
abort on a non-multiple-of-16 length as ciphertext stealing
is not implemented.