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.\"
.IX Title "BN_bn2bin 3"
.TH BN_bn2bin 3 "2020-12-10" "1.1.1i" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
BN_bn2binpad,
BN_bn2bin, BN_bin2bn, BN_bn2lebinpad, BN_lebin2bn, 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>
\&
\& int BN_bn2bin(const BIGNUM *a, unsigned char *to);
\& int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen);
\& BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret);
\&
\& int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen);
\& BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret);
\&
\& 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);
\&
\& int BN_print(BIO *fp, const BIGNUM *a);
\& int BN_print_fp(FILE *fp, const BIGNUM *a);
\&
\& 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"
\&\fBBN_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
\&\fBBN_bn2binpad()\fR also converts the absolute value of \fBa\fR into big-endian form
and stores it at \fBto\fR. \fBtolen\fR indicates the length of the output buffer
\&\fBto\fR. The result is padded with zeros if necessary. If \fBtolen\fR is less than
BN_num_bytes(\fBa\fR) an error is returned.
.PP
\&\fBBN_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
\&\fBBN_bn2lebinpad()\fR and \fBBN_lebin2bn()\fR are identical to \fBBN_bn2binpad()\fR and
\&\fBBN_bin2bn()\fR except the buffer is in little-endian format.
.PP
\&\fBBN_bn2hex()\fR and \fBBN_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 \fBOPENSSL_free()\fR.
.PP
\&\fBBN_hex2bn()\fR takes as many characters as possible from the string \fBstr\fR,
including the leading character '\-' which means negative, to form a valid
hexadecimal number representation and converts them to a \fB\s-1BIGNUM\s0\fR and
stores it in **\fBa\fR. If *\fBa\fR is \s-1NULL,\s0 a new \fB\s-1BIGNUM\s0\fR is created. If
\&\fBa\fR is \s-1NULL,\s0 it only computes the length of valid representation.
A \*(L"negative zero\*(R" is converted to zero.
\&\fBBN_dec2bn()\fR is the same using the decimal system.
.PP
\&\fBBN_print()\fR and \fBBN_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
\&\fBBN_bn2mpi()\fR and \fBBN_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
\&\fBBN_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
\&\fBBN_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"
\&\fBBN_bn2bin()\fR returns the length of the big-endian number placed at \fBto\fR.
\&\fBBN_bin2bn()\fR returns the \fB\s-1BIGNUM\s0\fR, \s-1NULL\s0 on error.
.PP
\&\fBBN_bn2binpad()\fR returns the number of bytes written or \-1 if the supplied
buffer is too small.
.PP
\&\fBBN_bn2hex()\fR and \fBBN_bn2dec()\fR return a null-terminated string, or \s-1NULL\s0
on error. \fBBN_hex2bn()\fR and \fBBN_dec2bn()\fR return the number of characters
used in parsing, or 0 on error, in which
case no new \fB\s-1BIGNUM\s0\fR will be created.
.PP
\&\fBBN_print_fp()\fR and \fBBN_print()\fR return 1 on success, 0 on write errors.
.PP
\&\fBBN_bn2mpi()\fR returns the length of the representation. \fBBN_mpi2bn()\fR
returns the \fB\s-1BIGNUM\s0\fR, and \s-1NULL\s0 on error.
.PP
The error codes can be obtained by \fBERR_get_error\fR\|(3).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBERR_get_error\fR\|(3), \fBBN_zero\fR\|(3),
\&\fBASN1_INTEGER_to_BN\fR\|(3),
\&\fBBN_num_bytes\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.