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137 .IX Title "BN_bn2bin 3"
138 .TH BN_bn2bin 3 "2009-07-19" "1.0.1n" "OpenSSL"
139 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
140 .\" way too many mistakes in technical documents.
144 BN_bn2bin, BN_bin2bn, BN_bn2hex, BN_bn2dec, BN_hex2bn, BN_dec2bn,
145 BN_print, BN_print_fp, BN_bn2mpi, BN_mpi2bn \- format conversions
149 .IX Header "SYNOPSIS"
151 \& #include <openssl/bn.h>
153 \& int BN_bn2bin(const BIGNUM *a, unsigned char *to);
154 \& BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret);
156 \& char *BN_bn2hex(const BIGNUM *a);
157 \& char *BN_bn2dec(const BIGNUM *a);
158 \& int BN_hex2bn(BIGNUM **a, const char *str);
159 \& int BN_dec2bn(BIGNUM **a, const char *str);
161 \& int BN_print(BIO *fp, const BIGNUM *a);
162 \& int BN_print_fp(FILE *fp, const BIGNUM *a);
164 \& int BN_bn2mpi(const BIGNUM *a, unsigned char *to);
165 \& BIGNUM *BN_mpi2bn(unsigned char *s, int len, BIGNUM *ret);
168 .IX Header "DESCRIPTION"
169 \&\fIBN_bn2bin()\fR converts the absolute value of \fBa\fR into big-endian form
170 and stores it at \fBto\fR. \fBto\fR must point to BN_num_bytes(\fBa\fR) bytes of
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_bn2hex()\fR and \fIBN_bn2dec()\fR return printable strings containing the
178 hexadecimal and decimal encoding of \fBa\fR respectively. For negative
179 numbers, the string is prefaced with a leading '\-'. The string must be
180 freed later using \fIOPENSSL_free()\fR.
182 \&\fIBN_hex2bn()\fR converts the string \fBstr\fR containing a hexadecimal number
183 to a \fB\s-1BIGNUM\s0\fR and stores it in **\fBbn\fR. If *\fBbn\fR is \s-1NULL,\s0 a new
184 \&\fB\s-1BIGNUM\s0\fR is created. If \fBbn\fR is \s-1NULL,\s0 it only computes the number's
185 length in hexadecimal digits. If the string starts with '\-', the
186 number is negative. \fIBN_dec2bn()\fR is the same using the decimal system.
188 \&\fIBN_print()\fR and \fIBN_print_fp()\fR write the hexadecimal encoding of \fBa\fR,
189 with a leading '\-' for negative numbers, to the \fB\s-1BIO\s0\fR or \fB\s-1FILE\s0\fR
192 \&\fIBN_bn2mpi()\fR and \fIBN_mpi2bn()\fR convert \fB\s-1BIGNUM\s0\fRs from and to a format
193 that consists of the number's length in bytes represented as a 4\-byte
194 big-endian number, and the number itself in big-endian format, where
195 the most significant bit signals a negative number (the representation
196 of numbers with the \s-1MSB\s0 set is prefixed with null byte).
198 \&\fIBN_bn2mpi()\fR stores the representation of \fBa\fR at \fBto\fR, where \fBto\fR
199 must be large enough to hold the result. The size can be determined by
200 calling BN_bn2mpi(\fBa\fR, \s-1NULL\s0).
202 \&\fIBN_mpi2bn()\fR converts the \fBlen\fR bytes long representation at \fBs\fR to
203 a \fB\s-1BIGNUM\s0\fR and stores it at \fBret\fR, or in a newly allocated \fB\s-1BIGNUM\s0\fR
204 if \fBret\fR is \s-1NULL.\s0
206 .IX Header "RETURN VALUES"
207 \&\fIBN_bn2bin()\fR returns the length of the big-endian number placed at \fBto\fR.
208 \&\fIBN_bin2bn()\fR returns the \fB\s-1BIGNUM\s0\fR, \s-1NULL\s0 on error.
210 \&\fIBN_bn2hex()\fR and \fIBN_bn2dec()\fR return a null-terminated string, or \s-1NULL\s0
211 on error. \fIBN_hex2bn()\fR and \fIBN_dec2bn()\fR return the number's length in
212 hexadecimal or decimal digits, and 0 on error.
214 \&\fIBN_print_fp()\fR and \fIBN_print()\fR return 1 on success, 0 on write errors.
216 \&\fIBN_bn2mpi()\fR returns the length of the representation. \fIBN_mpi2bn()\fR
217 returns the \fB\s-1BIGNUM\s0\fR, and \s-1NULL\s0 on error.
219 The error codes can be obtained by \fIERR_get_error\fR\|(3).
221 .IX Header "SEE ALSO"
222 \&\fIopenssl_bn\fR\|(3), \fIERR_get_error\fR\|(3), \fIBN_zero\fR\|(3),
223 \&\fIASN1_INTEGER_to_BN\fR\|(3),
224 \&\fIBN_num_bytes\fR\|(3)
227 \&\fIBN_bn2bin()\fR, \fIBN_bin2bn()\fR, \fIBN_print_fp()\fR and \fIBN_print()\fR are available
228 in all versions of SSLeay and OpenSSL.
230 \&\fIBN_bn2hex()\fR, \fIBN_bn2dec()\fR, \fIBN_hex2bn()\fR, \fIBN_dec2bn()\fR, \fIBN_bn2mpi()\fR and
231 \&\fIBN_mpi2bn()\fR were added in SSLeay 0.9.0.