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131 .IX Title "BN_BN2BIN 3"
132 .TH BN_BN2BIN 3 "2018-09-11" "1.1.1" "OpenSSL"
133 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
134 .\" way too many mistakes in technical documents.
138 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
140 .IX Header "SYNOPSIS"
142 \& #include <openssl/bn.h>
144 \& int BN_bn2bin(const BIGNUM *a, unsigned char *to);
145 \& int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen);
146 \& BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret);
148 \& int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen);
149 \& BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret);
151 \& char *BN_bn2hex(const BIGNUM *a);
152 \& char *BN_bn2dec(const BIGNUM *a);
153 \& int BN_hex2bn(BIGNUM **a, const char *str);
154 \& int BN_dec2bn(BIGNUM **a, const char *str);
156 \& int BN_print(BIO *fp, const BIGNUM *a);
157 \& int BN_print_fp(FILE *fp, const BIGNUM *a);
159 \& int BN_bn2mpi(const BIGNUM *a, unsigned char *to);
160 \& BIGNUM *BN_mpi2bn(unsigned char *s, int len, BIGNUM *ret);
163 .IX Header "DESCRIPTION"
164 \&\fIBN_bn2bin()\fR converts the absolute value of \fBa\fR into big-endian form
165 and stores it at \fBto\fR. \fBto\fR must point to BN_num_bytes(\fBa\fR) bytes of
168 \&\fIBN_bn2binpad()\fR also converts the absolute value of \fBa\fR into big-endian form
169 and stores it at \fBto\fR. \fBtolen\fR indicates the length of the output buffer
170 \&\fBto\fR. The result is padded with zeroes if necessary. If \fBtolen\fR is less than
171 BN_num_bytes(\fBa\fR) an error is returned.
173 \&\fIBN_bin2bn()\fR converts the positive integer in big-endian form of length
174 \&\fBlen\fR at \fBs\fR into a \fB\s-1BIGNUM\s0\fR and places it in \fBret\fR. If \fBret\fR is
175 \&\s-1NULL,\s0 a new \fB\s-1BIGNUM\s0\fR is created.
177 \&\fIBN_bn2lebinpad()\fR and \fIBN_lebin2bn()\fR are identical to \fIBN_bn2binpad()\fR and
178 \&\fIBN_bin2bn()\fR except the buffer is in little-endian format.
180 \&\fIBN_bn2hex()\fR and \fIBN_bn2dec()\fR return printable strings containing the
181 hexadecimal and decimal encoding of \fBa\fR respectively. For negative
182 numbers, the string is prefaced with a leading '\-'. The string must be
183 freed later using \fIOPENSSL_free()\fR.
185 \&\fIBN_hex2bn()\fR takes as many characters as possible from the string \fBstr\fR,
186 including the leading character '\-' which means negative, to form a valid
187 hexadecimal number representation and converts them to a \fB\s-1BIGNUM\s0\fR and
188 stores it in **\fBa\fR. If *\fBa\fR is \s-1NULL,\s0 a new \fB\s-1BIGNUM\s0\fR is created. If
189 \&\fBa\fR is \s-1NULL,\s0 it only computes the length of valid representation.
190 A \*(L"negative zero\*(R" is converted to zero.
191 \&\fIBN_dec2bn()\fR is the same using the decimal system.
193 \&\fIBN_print()\fR and \fIBN_print_fp()\fR write the hexadecimal encoding of \fBa\fR,
194 with a leading '\-' for negative numbers, to the \fB\s-1BIO\s0\fR or \fB\s-1FILE\s0\fR
197 \&\fIBN_bn2mpi()\fR and \fIBN_mpi2bn()\fR convert \fB\s-1BIGNUM\s0\fRs from and to a format
198 that consists of the number's length in bytes represented as a 4\-byte
199 big-endian number, and the number itself in big-endian format, where
200 the most significant bit signals a negative number (the representation
201 of numbers with the \s-1MSB\s0 set is prefixed with null byte).
203 \&\fIBN_bn2mpi()\fR stores the representation of \fBa\fR at \fBto\fR, where \fBto\fR
204 must be large enough to hold the result. The size can be determined by
205 calling BN_bn2mpi(\fBa\fR, \s-1NULL\s0).
207 \&\fIBN_mpi2bn()\fR converts the \fBlen\fR bytes long representation at \fBs\fR to
208 a \fB\s-1BIGNUM\s0\fR and stores it at \fBret\fR, or in a newly allocated \fB\s-1BIGNUM\s0\fR
209 if \fBret\fR is \s-1NULL.\s0
211 .IX Header "RETURN VALUES"
212 \&\fIBN_bn2bin()\fR returns the length of the big-endian number placed at \fBto\fR.
213 \&\fIBN_bin2bn()\fR returns the \fB\s-1BIGNUM\s0\fR, \s-1NULL\s0 on error.
215 \&\fIBN_bn2binpad()\fR returns the number of bytes written or \-1 if the supplied
218 \&\fIBN_bn2hex()\fR and \fIBN_bn2dec()\fR return a null-terminated string, or \s-1NULL\s0
219 on error. \fIBN_hex2bn()\fR and \fIBN_dec2bn()\fR return the number of characters
220 used in parsing, or 0 on error, in which
221 case no new \fB\s-1BIGNUM\s0\fR will be created.
223 \&\fIBN_print_fp()\fR and \fIBN_print()\fR return 1 on success, 0 on write errors.
225 \&\fIBN_bn2mpi()\fR returns the length of the representation. \fIBN_mpi2bn()\fR
226 returns the \fB\s-1BIGNUM\s0\fR, and \s-1NULL\s0 on error.
228 The error codes can be obtained by \fIERR_get_error\fR\|(3).
230 .IX Header "SEE ALSO"
231 \&\fIERR_get_error\fR\|(3), \fIBN_zero\fR\|(3),
232 \&\fIASN1_INTEGER_to_BN\fR\|(3),
233 \&\fIBN_num_bytes\fR\|(3)
235 .IX Header "COPYRIGHT"
236 Copyright 2000\-2018 The OpenSSL Project Authors. All Rights Reserved.
238 Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
239 this file except in compliance with the License. You can obtain a copy
240 in the file \s-1LICENSE\s0 in the source distribution or at
241 <https://www.openssl.org/source/license.html>.