.\" $OpenBSD: BN_bn2bin.3,v 1.16 2023/07/09 06:45:03 tb Exp $ .\" full merge up to: OpenSSL 24a535ea Sep 22 13:14:20 2020 +0100 .\" .\" This file was written by Ulf Moeller .\" and Dr. Stephen Henson . .\" Copyright (c) 2000, 2002, 2016 The OpenSSL Project. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" .\" .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to .\" endorse or promote products derived from this software without .\" prior written permission. For written permission, please contact .\" openssl-core@openssl.org. .\" .\" 5. Products derived from this software may not be called "OpenSSL" .\" nor may "OpenSSL" appear in their names without prior written .\" permission of the OpenSSL Project. .\" .\" 6. 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IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: July 9 2023 $ .Dt BN_BN2BIN 3 .Os .Sh NAME .Nm BN_bn2bin , .Nm BN_bn2binpad , .Nm BN_bin2bn , .Nm BN_bn2lebinpad , .Nm BN_lebin2bn , .Nm BN_bn2hex , .Nm BN_bn2dec , .Nm BN_hex2bn , .Nm BN_dec2bn , .Nm BN_asc2bn , .Nm BN_print , .Nm BN_print_fp , .Nm BN_bn2mpi , .Nm BN_mpi2bn .Nd format conversions .Sh SYNOPSIS .In openssl/bn.h .Ft int .Fo BN_bn2bin .Fa "const BIGNUM *a" .Fa "unsigned char *to" .Fc .Ft int .Fo BN_bn2binpad .Fa "const BIGNUM *a" .Fa "unsigned char *to" .Fa "int tolen" .Fc .Ft BIGNUM * .Fo BN_bin2bn .Fa "const unsigned char *s" .Fa "int len" .Fa "BIGNUM *ret" .Fc .Ft int .Fo BN_bn2lebinpad .Fa "const BIGNUM *a" .Fa "unsigned char *to" .Fa "int tolen" .Fc .Ft BIGNUM * .Fo BN_lebin2bn .Fa "const unsigned char *s" .Fa "int len" .Fa "BIGNUM *ret" .Fc .Ft char * .Fo BN_bn2hex .Fa "const BIGNUM *a" .Fc .Ft char * .Fo BN_bn2dec .Fa "const BIGNUM *a" .Fc .Ft int .Fo BN_hex2bn .Fa "BIGNUM **ap" .Fa "const char *str" .Fc .Ft int .Fo BN_dec2bn .Fa "BIGNUM **ap" .Fa "const char *str" .Fc .Ft int .Fo BN_asc2bn .Fa "BIGNUM **ap" .Fa "const char *str" .Fc .Ft int .Fo BN_print .Fa "BIO *fp" .Fa "const BIGNUM *a" .Fc .Ft int .Fo BN_print_fp .Fa "FILE *fp" .Fa "const BIGNUM *a" .Fc .Ft int .Fo BN_bn2mpi .Fa "const BIGNUM *a" .Fa "unsigned char *to" .Fc .Ft BIGNUM * .Fo BN_mpi2bn .Fa "unsigned char *s" .Fa "int len" .Fa "BIGNUM *ret" .Fc .Sh DESCRIPTION .Fn BN_bn2bin converts the absolute value of .Fa a into big-endian form and stores it at .Fa to . .Fa to must point to .Fn BN_num_bytes a bytes of memory. .Pp .Fn BN_bn2binpad also converts the absolute value of .Fa a into big-endian form and stores it at .Fa to . .Fa tolen indicates the length of the output buffer .Pf * Fa to . The result is padded with zeros if necessary. If .Fa tolen is less than .Fn BN_num_bytes a , an error is returned. .Pp .Fn BN_bin2bn converts the positive integer in big-endian form of length .Fa len at .Fa s into a .Vt BIGNUM and places it in .Fa ret . If .Fa ret is .Dv NULL , a new .Vt BIGNUM is created. .Pp .Fn BN_bn2lebinpad and .Fn BN_lebin2bn are identical to .Fn BN_bn2binpad and .Fn BN_bin2bn except the buffer .Pf * Fa to is in little-endian format. .Pp .Fn BN_bn2hex and .Fn BN_bn2dec return printable strings containing the hexadecimal and decimal encoding of .Fa a respectively. For negative numbers, the string is prefaced with a leading minus sign. The string must be freed later using .Xr free 3 . .Pp .Fn BN_hex2bn interprets .Fa str as a hexadecimal number. The string may start with a minus sign .Pq Sq - . Conversion stops at the first byte that is not a hexadecimal digit. The number is converted to a .Vt BIGNUM and stored in .Pf ** Fa ap . If .Pf * Fa ap is .Dv NULL , a new .Vt BIGNUM is created. If .Fa ap is .Dv NULL , it only computes the number's length in hexadecimal digits, also counting the leading minus sign if there is one. A "negative zero" is converted to zero. .Fn BN_dec2bn is the same using the decimal system. .Fn BN_asc2bn infers the number base from an optional prefix. If .Fa str starts with .Qq 0x or .Qq 0X , it calls .Fn BN_hex2bn , otherwise .Fn BN_dec2bn . If the number is negative, the minus sign can be given before or after the prefix. .Pp .Fn BN_print and .Fn BN_print_fp write the hexadecimal encoding of .Fa a , with a leading minus sign for negative numbers, to the .Vt BIO or .Vt FILE .Fa fp . .Pp .Fn BN_bn2mpi and .Fn BN_mpi2bn convert .Vt BIGNUM Ns s 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 MSB set is prefixed with a NUL byte). .Pp .Fn BN_bn2mpi stores the representation of .Fa a at .Fa to , where .Pf * Fa to must be large enough to hold the result. The size can be determined by calling .Fn BN_bn2mpi a NULL . .Pp .Fn BN_mpi2bn converts the .Fa len bytes long representation at .Fa s to a .Vt BIGNUM and stores it at .Fa ret , or in a newly allocated .Vt BIGNUM if .Fa ret is .Dv NULL . .Sh RETURN VALUES .Fn BN_bn2bin returns the length of the big-endian number placed at .Fa to . .Pp .Fn BN_bn2binpad and .Fn BN_bn2lebinpad return the number of bytes written or \-1 if the supplied buffer is too small. .Pp .Fn BN_bin2bn and .Fn BN_lebin2bn return the .Vt BIGNUM , or .Dv NULL on error. .Pp .Fn BN_bn2hex and .Fn BN_bn2dec return a NUL-terminated string, or .Dv NULL on error. .Fn BN_hex2bn and .Fn BN_dec2bn return the number's length in hexadecimal or decimal digits, also counting the leading minus sign if there is one, or 0 on error, in which case no new .Vt BIGNUM is created. .Fn BN_asc2bn returns 1 on success or 0 on error, in which case no new .Vt BIGNUM is created. .Pp .Fn BN_print_fp and .Fn BN_print return 1 on success, 0 on write errors. .Pp .Fn BN_bn2mpi returns the length of the representation. .Fn BN_mpi2bn returns the .Vt BIGNUM , or .Dv NULL on error. .Pp The error codes can be obtained by .Xr ERR_get_error 3 . .Sh SEE ALSO .Xr ASN1_INTEGER_to_BN 3 , .Xr BN_new 3 , .Xr BN_num_bytes 3 , .Xr BN_zero 3 .Sh HISTORY .Fn BN_bn2bin , .Fn BN_bin2bn , and .Fn BN_print first appeared in SSLeay 0.5.1. .Fn BN_print_fp first appeared in SSLeay 0.6.0. .Fn BN_bn2hex , .Fn BN_bn2dec , .Fn BN_hex2bn , .Fn BN_dec2bn , .Fn BN_bn2mpi , and .Fn BN_mpi2bn first appeared in SSLeay 0.9.0. All these functions have been available since .Ox 2.4 . .Pp .Fn BN_asc2bin first appeared in OpenSSL 1.0.0 and has been available since .Ox 4.9 . .Pp .Fn BN_bn2binpad , .Fn BN_bn2lebinpad , and .Fn BN_lebin2bn first appeared in OpenSSL 1.1.0 and have been available since .Ox 7.0 .