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HMAC_Init_ex.3
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.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.32 .\" .\" Standard preamble: .\" ======================================================================== .de Sh \" Subsection heading .br .if t .Sp .ne 5 .PP \fB\\$1\fR .PP .. .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. | will give a .\" real vertical bar. \*(C+ will give a nicer C++. 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If \fBmd\fR is \s-1NULL\s0, the digest is placed in a static array. The size of the output is placed in \fBmd_len\fR, unless it is \fB\s-1NULL\s0\fR. .PP \&\fBevp_md\fR can be \fIEVP_sha1()\fR, \fIEVP_ripemd160()\fR etc. .PP \&\fIHMAC_CTX_init()\fR initialises a \fB\s-1HMAC_CTX\s0\fR before first use. It must be called. .PP \&\fIHMAC_CTX_cleanup()\fR erases the key and other data from the \fB\s-1HMAC_CTX\s0\fR and releases any associated resources. It must be called when an \&\fB\s-1HMAC_CTX\s0\fR is no longer required. .PP \&\fIHMAC_cleanup()\fR is an alias for \fIHMAC_CTX_cleanup()\fR included for back compatibility with 0.9.6b, it is deprecated. .PP The following functions may be used if the message is not completely stored in memory: .PP \&\fIHMAC_Init()\fR initializes a \fB\s-1HMAC_CTX\s0\fR structure to use the hash function \fBevp_md\fR and the key \fBkey\fR which is \fBkey_len\fR bytes long. It is deprecated and only included for backward compatibility with OpenSSL 0.9.6b. .PP \&\fIHMAC_Init_ex()\fR initializes or reuses a \fB\s-1HMAC_CTX\s0\fR structure to use the hash function \fBevp_md\fR and key \fBkey\fR. If both are \s-1NULL\s0 (or \fBevp_md\fR is the same as the previous digest used by \fBctx\fR and \fBkey\fR is \s-1NULL\s0) the existing key is reused. \fBctx\fR must have been created with \fIHMAC_CTX_new()\fR before the first use of an \fB\s-1HMAC_CTX\s0\fR in this function. \fBN.B. \f(BIHMAC_Init()\fB had this undocumented behaviour in previous versions of OpenSSL \- failure to switch to \f(BIHMAC_Init_ex()\fB in programs that expect it will cause them to stop working\fR. .PP \&\fB\s-1NB:\s0 if \f(BIHMAC_Init_ex()\fB is called with \fBkey\fB \s-1NULL\s0 and \fBevp_md\fB is not the same as the previous digest used by \fBctx\fB then an error is returned because reuse of an existing key with a different digest is not supported.\fR .PP \&\fIHMAC_Update()\fR can be called repeatedly with chunks of the message to be authenticated (\fBlen\fR bytes at \fBdata\fR). .PP \&\fIHMAC_Final()\fR places the message authentication code in \fBmd\fR, which must have space for the hash function output. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\s-1\fIHMAC\s0()\fR returns a pointer to the message authentication code or \s-1NULL\s0 if an error occurred. .PP \&\fIHMAC_Init_ex()\fR, \fIHMAC_Update()\fR and \fIHMAC_Final()\fR return 1 for success or 0 if an error occurred. .PP \&\fIHMAC_CTX_init()\fR and \fIHMAC_CTX_cleanup()\fR do not return values. .SH "CONFORMING TO" .IX Header "CONFORMING TO" \&\s-1RFC\s0 2104 .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fIsha\fR\|(3), \fIevp\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" \&\s-1\fIHMAC\s0()\fR, \fIHMAC_Init()\fR, \fIHMAC_Update()\fR, \fIHMAC_Final()\fR and \fIHMAC_cleanup()\fR are available since SSLeay 0.9.0. .PP \&\fIHMAC_CTX_init()\fR, \fIHMAC_Init_ex()\fR and \fIHMAC_CTX_cleanup()\fR are available since OpenSSL 0.9.7. .PP \&\fIHMAC_Init_ex()\fR, \fIHMAC_Update()\fR and \fIHMAC_Final()\fR did not return values in versions of OpenSSL before 1.0.0.