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.\" ========================================================================
.\"
.IX Title "RSA_sign 3"
.TH RSA_sign 3 2019-12-20 1.0.2u OpenSSL
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH NAME
RSA_sign, RSA_verify \- RSA signatures
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/rsa.h>
\&
\& int RSA_sign(int type, const unsigned char *m, unsigned int m_len,
\&    unsigned char *sigret, unsigned int *siglen, RSA *rsa);
\&
\& int RSA_verify(int type, const unsigned char *m, unsigned int m_len,
\&    unsigned char *sigbuf, unsigned int siglen, RSA *rsa);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\fBRSA_sign()\fR signs the message digest \fBm\fR of size \fBm_len\fR using the
private key \fBrsa\fR as specified in PKCS #1 v2.0. It stores the
signature in \fBsigret\fR and the signature size in \fBsiglen\fR. \fBsigret\fR
must point to RSA_size(\fBrsa\fR) bytes of memory.
Note that PKCS #1 adds meta-data, placing limits on the size of the
key that can be used.
See \fBRSA_private_encrypt\fR\|(3) for lower-level
operations.
.PP
\&\fBtype\fR denotes the message digest algorithm that was used to generate
\&\fBm\fR. It usually is one of \fBNID_sha1\fR, \fBNID_ripemd160\fR and \fBNID_md5\fR;
see \fBobjects\fR\|(3) for details. If \fBtype\fR is \fBNID_md5_sha1\fR,
an SSL signature (MD5 and SHA1 message digests with PKCS #1 padding
and no algorithm identifier) is created.
.PP
\&\fBRSA_verify()\fR verifies that the signature \fBsigbuf\fR of size \fBsiglen\fR
matches a given message digest \fBm\fR of size \fBm_len\fR. \fBtype\fR denotes
the message digest algorithm that was used to generate the signature.
\&\fBrsa\fR is the signer's public key.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBRSA_sign()\fR returns 1 on success, 0 otherwise.  \fBRSA_verify()\fR returns 1
on successful verification, 0 otherwise.
.PP
The error codes can be obtained by \fBERR_get_error\fR\|(3).
.SH BUGS
.IX Header "BUGS"
Certain signatures with an improper algorithm identifier are accepted
for compatibility with SSLeay 0.4.5 :\-)
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
SSL, PKCS #1 v2.0
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBERR_get_error\fR\|(3), \fBobjects\fR\|(3),
\&\fBrsa\fR\|(3), \fBRSA_private_encrypt\fR\|(3),
\&\fBRSA_public_decrypt\fR\|(3)
.SH HISTORY
.IX Header "HISTORY"
\&\fBRSA_sign()\fR and \fBRSA_verify()\fR are available in all versions of SSLeay
and OpenSSL.