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.IX Title "BN_bn2bin 3"
.TH BN_bn2bin 3 "0.9.7b" "2002-09-25" "OpenSSL"
.UC
.SH "NAME"
BN_bn2bin, BN_bin2bn, BN_bn2hex, BN_bn2dec, BN_hex2bn, BN_dec2bn,
BN_print, BN_print_fp, BN_bn2mpi, BN_mpi2bn \- format conversions
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/bn.h>
.Ve
.Vb 2
\& int BN_bn2bin(const BIGNUM *a, unsigned char *to);
\& BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret);
.Ve
.Vb 4
\& char *BN_bn2hex(const BIGNUM *a);
\& char *BN_bn2dec(const BIGNUM *a);
\& int BN_hex2bn(BIGNUM **a, const char *str);
\& int BN_dec2bn(BIGNUM **a, const char *str);
.Ve
.Vb 2
\& int BN_print(BIO *fp, const BIGNUM *a);
\& int BN_print_fp(FILE *fp, const BIGNUM *a);
.Ve
.Vb 2
\& int BN_bn2mpi(const BIGNUM *a, unsigned char *to);
\& BIGNUM *BN_mpi2bn(unsigned char *s, int len, BIGNUM *ret);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fIBN_bn2bin()\fR converts the absolute value of \fBa\fR into big-endian form
and stores it at \fBto\fR. \fBto\fR must point to BN_num_bytes(\fBa\fR) bytes of
memory.
.PP
\&\fIBN_bin2bn()\fR converts the positive integer in big-endian form of length
\&\fBlen\fR at \fBs\fR into a \fB\s-1BIGNUM\s0\fR and places it in \fBret\fR. If \fBret\fR is
\&\s-1NULL\s0, a new \fB\s-1BIGNUM\s0\fR is created.
.PP
\&\fIBN_bn2hex()\fR and \fIBN_bn2dec()\fR return printable strings containing the
hexadecimal and decimal encoding of \fBa\fR respectively. For negative
numbers, the string is prefaced with a leading '\-'. The string must be
freed later using \fIOPENSSL_free()\fR.
.PP
\&\fIBN_hex2bn()\fR converts the string \fBstr\fR containing a hexadecimal number
to a \fB\s-1BIGNUM\s0\fR and stores it in **\fBbn\fR. If *\fBbn\fR is \s-1NULL\s0, a new
\&\fB\s-1BIGNUM\s0\fR is created. If \fBbn\fR is \s-1NULL\s0, it only computes the number's
length in hexadecimal digits. If the string starts with '\-', the
number is negative. \fIBN_dec2bn()\fR is the same using the decimal system.
.PP
\&\fIBN_print()\fR and \fIBN_print_fp()\fR write the hexadecimal encoding of \fBa\fR,
with a leading '\-' for negative numbers, to the \fB\s-1BIO\s0\fR or \fB\s-1FILE\s0\fR
\&\fBfp\fR.
.PP
\&\fIBN_bn2mpi()\fR and \fIBN_mpi2bn()\fR convert \fB\s-1BIGNUM\s0\fRs from and to a format
that consists of the number's length in bytes represented as a 4\-byte
big-endian number, and the number itself in big-endian format, where
the most significant bit signals a negative number (the representation
of numbers with the \s-1MSB\s0 set is prefixed with null byte).
.PP
\&\fIBN_bn2mpi()\fR stores the representation of \fBa\fR at \fBto\fR, where \fBto\fR
must be large enough to hold the result. The size can be determined by
calling BN_bn2mpi(\fBa\fR, \s-1NULL\s0).
.PP
\&\fIBN_mpi2bn()\fR converts the \fBlen\fR bytes long representation at \fBs\fR to
a \fB\s-1BIGNUM\s0\fR and stores it at \fBret\fR, or in a newly allocated \fB\s-1BIGNUM\s0\fR
if \fBret\fR is \s-1NULL\s0.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fIBN_bn2bin()\fR returns the length of the big-endian number placed at \fBto\fR.
\&\fIBN_bin2bn()\fR returns the \fB\s-1BIGNUM\s0\fR, \s-1NULL\s0 on error.
.PP
\&\fIBN_bn2hex()\fR and \fIBN_bn2dec()\fR return a null-terminated string, or \s-1NULL\s0
on error. \fIBN_hex2bn()\fR and \fIBN_dec2bn()\fR return the number's length in
hexadecimal or decimal digits, and 0 on error.
.PP
\&\fIBN_print_fp()\fR and \fIBN_print()\fR return 1 on success, 0 on write errors.
.PP
\&\fIBN_bn2mpi()\fR returns the length of the representation. \fIBN_mpi2bn()\fR
returns the \fB\s-1BIGNUM\s0\fR, and \s-1NULL\s0 on error.
.PP
The error codes can be obtained by ERR_get_error(3).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
openssl_bn(3), ERR_get_error(3), BN_zero(3),
ASN1_INTEGER_to_BN(3),
BN_num_bytes(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fIBN_bn2bin()\fR, \fIBN_bin2bn()\fR, \fIBN_print_fp()\fR and \fIBN_print()\fR are available
in all versions of SSLeay and OpenSSL.
.PP
\&\fIBN_bn2hex()\fR, \fIBN_bn2dec()\fR, \fIBN_hex2bn()\fR, \fIBN_dec2bn()\fR, \fIBN_bn2mpi()\fR and
\&\fIBN_mpi2bn()\fR were added in SSLeay 0.9.0.