Switch from OpenSSL 0.9.7d to 0.9.7e.
[dragonfly.git] / secure / lib / libcrypto / man / hmac.3
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2''' $RCSfile$$Revision$$Date$
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34'''
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37''' string Tr holds user defined translation string.
38''' Bell System Logo is used as a dummy character.
39'''
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42.ds -- \(*W-
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50''' such as .IP and .SH, which do another additional levels of
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80.\" If the F register is turned on, we'll generate
81.\" index entries out stderr for the following things:
82.\" TH Title
83.\" SH Header
84.\" Sh Subsection
85.\" Ip Item
86.\" X<> Xref (embedded
87.\" Of course, you have to process the output yourself
88.\" in some meaninful fashion.
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96.TH hmac 3 "0.9.7d" "2/Sep/2004" "OpenSSL"
97.UC
98.if n .hy 0
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188.\}
189.rm #[ #] #H #V #F C
984263bc 190.SH "NAME"
74dab6c2 191HMAC, HMAC_Init, HMAC_Update, HMAC_Final, HMAC_cleanup \- HMAC message
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192authentication code
193.SH "SYNOPSIS"
74dab6c2 194.PP
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195.Vb 1
196\& #include <openssl/hmac.h>
197.Ve
198.Vb 3
199\& unsigned char *HMAC(const EVP_MD *evp_md, const void *key,
200\& int key_len, const unsigned char *d, int n,
201\& unsigned char *md, unsigned int *md_len);
202.Ve
203.Vb 1
204\& void HMAC_CTX_init(HMAC_CTX *ctx);
205.Ve
206.Vb 6
207\& void HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len,
208\& const EVP_MD *md);
209\& void HMAC_Init_ex(HMAC_CTX *ctx, const void *key, int key_len,
210\& const EVP_MD *md);
211\& void HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len);
212\& void HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len);
213.Ve
214.Vb 2
215\& void HMAC_CTX_cleanup(HMAC_CTX *ctx);
216\& void HMAC_cleanup(HMAC_CTX *ctx);
217.Ve
218.SH "DESCRIPTION"
74dab6c2 219HMAC is a MAC (message authentication code), i.e. a keyed hash
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220function used for message authentication, which is based on a hash
221function.
222.PP
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223\fIHMAC()\fR computes the message authentication code of the \fBn\fR bytes at
224\fBd\fR using the hash function \fBevp_md\fR and the key \fBkey\fR which is
225\fBkey_len\fR bytes long.
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226.PP
227It places the result in \fBmd\fR (which must have space for the output of
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228the hash function, which is no more than \fBEVP_MAX_MD_SIZE\fR bytes).
229If \fBmd\fR is NULL, the digest is placed in a static array. The size of
230the output is placed in \fBmd_len\fR, unless it is \fBNULL\fR.
984263bc 231.PP
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232\fBevp_md\fR can be \fIEVP_sha1()\fR, \fIEVP_ripemd160()\fR etc.
233\fBkey\fR and \fBevp_md\fR may be \fBNULL\fR if a key and hash function have
234been set in a previous call to \fIHMAC_Init()\fR for that \fBHMAC_CTX\fR.
984263bc 235.PP
74dab6c2 236\fIHMAC_CTX_init()\fR initialises a \fBHMAC_CTX\fR before first use. It must be
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237called.
238.PP
74dab6c2 239\fIHMAC_CTX_cleanup()\fR erases the key and other data from the \fBHMAC_CTX\fR
984263bc 240and releases any associated resources. It must be called when an
74dab6c2 241\fBHMAC_CTX\fR is no longer required.
984263bc 242.PP
74dab6c2 243\fIHMAC_cleanup()\fR is an alias for \fIHMAC_CTX_cleanup()\fR included for back
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244compatibility with 0.9.6b, it is deprecated.
245.PP
246The following functions may be used if the message is not completely
247stored in memory:
248.PP
74dab6c2 249\fIHMAC_Init()\fR initializes a \fBHMAC_CTX\fR structure to use the hash
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250function \fBevp_md\fR and the key \fBkey\fR which is \fBkey_len\fR bytes
251long. It is deprecated and only included for backward compatibility
252with OpenSSL 0.9.6b.
253.PP
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254\fIHMAC_Init_ex()\fR initializes or reuses a \fBHMAC_CTX\fR structure to use
255the function \fBevp_md\fR and key \fBkey\fR. Either can be NULL, in which
984263bc 256case the existing one will be reused. \fIHMAC_CTX_init()\fR must have been
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257called before the first use of an \fBHMAC_CTX\fR in this
258function. \fBN.B. HMAC_Init() had this undocumented behaviour in
259previous versions of OpenSSL \- failure to switch to HMAC_Init_ex() in
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260programs that expect it will cause them to stop working\fR.
261.PP
74dab6c2 262\fIHMAC_Update()\fR can be called repeatedly with chunks of the message to
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263be authenticated (\fBlen\fR bytes at \fBdata\fR).
264.PP
74dab6c2 265\fIHMAC_Final()\fR places the message authentication code in \fBmd\fR, which
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266must have space for the hash function output.
267.SH "RETURN VALUES"
74dab6c2 268\fIHMAC()\fR returns a pointer to the message authentication code.
984263bc 269.PP
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270\fIHMAC_CTX_init()\fR, \fIHMAC_Init_ex()\fR, \fIHMAC_Update()\fR, \fIHMAC_Final()\fR and
271\fIHMAC_CTX_cleanup()\fR do not return values.
984263bc 272.SH "CONFORMING TO"
74dab6c2 273RFC 2104
984263bc 274.SH "SEE ALSO"
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275sha(3), evp(3)
276.SH "HISTORY"
74dab6c2 277\fIHMAC()\fR, \fIHMAC_Init()\fR, \fIHMAC_Update()\fR, \fIHMAC_Final()\fR and \fIHMAC_cleanup()\fR
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278are available since SSLeay 0.9.0.
279.PP
74dab6c2 280\fIHMAC_CTX_init()\fR, \fIHMAC_Init_ex()\fR and \fIHMAC_CTX_cleanup()\fR are available
984263bc 281since OpenSSL 0.9.7.
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282
283.rn }` ''
284.IX Title "hmac 3"
285.IX Name "HMAC, HMAC_Init, HMAC_Update, HMAC_Final, HMAC_cleanup - HMAC message
286authentication code"
287
288.IX Header "NAME"
289
290.IX Header "SYNOPSIS"
291
292.IX Header "DESCRIPTION"
293
294.IX Header "RETURN VALUES"
295
296.IX Header "CONFORMING TO"
297
298.IX Header "SEE ALSO"
299
300.IX Header "HISTORY"
301