Updated: 2021/Apr/14


BN_bn2bin(3)                        OpenSSL                       BN_bn2bin(3)



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

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #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);

DESCRIPTION
       BN_bn2bin() converts the absolute value of a into big-endian form and
       stores it at to. to must point to BN_num_bytes(a) bytes of memory.

       BN_bn2binpad() also converts the absolute value of a into big-endian
       form and stores it at to. tolen indicates the length of the output
       buffer to. The result is padded with zeros if necessary. If tolen is
       less than BN_num_bytes(a) an error is returned.

       BN_bin2bn() converts the positive integer in big-endian form of length
       len at s into a BIGNUM and places it in ret. If ret is NULL, a new
       BIGNUM is created.

       BN_bn2lebinpad() and BN_lebin2bn() are identical to BN_bn2binpad() and
       BN_bin2bn() except the buffer is in little-endian format.

       BN_bn2hex() and BN_bn2dec() return printable strings containing the
       hexadecimal and decimal encoding of a respectively. For negative
       numbers, the string is prefaced with a leading '-'. The string must be
       freed later using OPENSSL_free().

       BN_hex2bn() takes as many characters as possible from the string str,
       including the leading character '-' which means negative, to form a
       valid hexadecimal number representation and converts them to a BIGNUM
       and stores it in **a. If *a is NULL, a new BIGNUM is created. If a is
       NULL, it only computes the length of valid representation.  A "negative
       zero" is converted to zero.  BN_dec2bn() is the same using the decimal
       system.

       BN_print() and BN_print_fp() write the hexadecimal encoding of a, with
       a leading '-' for negative numbers, to the BIO or FILE fp.

       BN_bn2mpi() and BN_mpi2bn() convert BIGNUMs 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 null byte).

       BN_bn2mpi() stores the representation of a at to, where to must be
       large enough to hold the result. The size can be determined by calling
       BN_bn2mpi(a, NULL).

       BN_mpi2bn() converts the len bytes long representation at s to a BIGNUM
       and stores it at ret, or in a newly allocated BIGNUM if ret is NULL.

RETURN VALUES
       BN_bn2bin() returns the length of the big-endian number placed at to.
       BN_bin2bn() returns the BIGNUM, NULL on error.

       BN_bn2binpad() returns the number of bytes written or -1 if the
       supplied buffer is too small.

       BN_bn2hex() and BN_bn2dec() return a null-terminated string, or NULL on
       error. BN_hex2bn() and BN_dec2bn() return the number of characters used
       in parsing, or 0 on error, in which case no new BIGNUM will be created.

       BN_print_fp() and BN_print() return 1 on success, 0 on write errors.

       BN_bn2mpi() returns the length of the representation. BN_mpi2bn()
       returns the BIGNUM, and NULL on error.

       The error codes can be obtained by ERR_get_error(3).

SEE ALSO
       ERR_get_error(3), BN_zero(3), ASN1_INTEGER_to_BN(3), BN_num_bytes(3)

COPYRIGHT
       Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.



1.1.1i                            2020-12-10                      BN_bn2bin(3)