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.\" ========================================================================
.\"
.IX Title "RSA_generate_key 3"
.TH RSA_generate_key 3 "2019-12-20" "1.0.2u" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
RSA_generate_key_ex, RSA_generate_key \- generate RSA key pair
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/rsa.h>
\&
\& int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);
.Ve
.PP
Deprecated:
.PP
.Vb 2
\& RSA *RSA_generate_key(int num, unsigned long e,
\&    void (*callback)(int,int,void *), void *cb_arg);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBRSA_generate_key_ex()\fR generates a key pair and stores it in the \fB\s-1RSA\s0\fR
structure provided in \fBrsa\fR. The pseudo-random number generator must
be seeded prior to calling \fBRSA_generate_key_ex()\fR.
.PP
The modulus size will be of length \fBbits\fR, and the public exponent will be
\&\fBe\fR. Key sizes with \fBnum\fR < 1024 should be considered insecure.
The exponent is an odd number, typically 3, 17 or 65537.
.PP
A callback function may be used to provide feedback about the
progress of the key generation. If \fBcb\fR is not \fB\s-1NULL\s0\fR, it
will be called as follows using the \fBBN_GENCB_call()\fR function
described on the \fBBN_generate_prime\fR\|(3) page.
.IP "\(bu" 4
While a random prime number is generated, it is called as
described in \fBBN_generate_prime\fR\|(3).
.IP "\(bu" 4
When the n\-th randomly generated prime is rejected as not
suitable for the key, \fBBN_GENCB_call(cb, 2, n)\fR is called.
.IP "\(bu" 4
When a random p has been found with p\-1 relatively prime to \fBe\fR,
it is called as \fBBN_GENCB_call(cb, 3, 0)\fR.
.PP
The process is then repeated for prime q with \fBBN_GENCB_call(cb, 3, 1)\fR.
.PP
RSA_generate_key is deprecated (new applications should use
RSA_generate_key_ex instead). RSA_generate_key works in the same way as
RSA_generate_key_ex except it uses \*(L"old style\*(R" call backs. See
\&\fBBN_generate_prime\fR\|(3) for further details.
.SH "RETURN VALUE"
.IX Header "RETURN VALUE"
If key generation fails, \fBRSA_generate_key()\fR returns \fB\s-1NULL\s0\fR.
.PP
The error codes can be obtained by \fBERR_get_error\fR\|(3).
.SH "BUGS"
.IX Header "BUGS"
\&\fBBN_GENCB_call(cb, 2, x)\fR is used with two different meanings.
.PP
\&\fBRSA_generate_key()\fR goes into an infinite loop for illegal input values.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBERR_get_error\fR\|(3), \fBrand\fR\|(3), \fBrsa\fR\|(3),
\&\fBRSA_free\fR\|(3), \fBBN_generate_prime\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
The \fBcb_arg\fR argument was added in SSLeay 0.9.0.