BN_bn2bin(3) — Subroutines

NAME

BN_bn2bin, BN_bin2bn, BN_bn2hex, BN_bn2dec, BN_hex2bn, BN_dec2bn, BN_print, BN_print_fp, BN_bn2mpi, BN_mpi2bn − Format conversions

SYNOPSIS

#include <openssl/bn.h>
int BN_bn2bin(
        const BIGNUM ∗a, unsigned char ∗to ); BIGNUM ∗BN_bin2bn(
        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

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

The BN_bin2bn() function 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.

The BN_bn2hex() and BN_bn2dec() functions 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() converts the string str containing a hexadecimal number to a BIGNUM and stores it in ∗∗bn. If ∗bn is NULL, a new BIGNUM is created. If bn is NULL, it only computes the number’s length in hexadecimal digits. If the string starts with ’-’, the number is negative. BN_dec2bn() is the same using the decimal system.

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

The BN_bn2mpi() and BN_mpi2bn() functions 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).

The BN_bn2mpi() function 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).

The BN_mpi2bn() function 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

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

The BN_bn2hex() and BN_bn2dec() functions return a null-terminated string, or NULL on error. The BN_hex2bn() and BN_dec2bn() functions return the number’s length in hexadecimal or decimal digits, and 0 on error.

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

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

The error codes can be obtained by using the ERR_get_error() function.

HISTORY

The BN_bn2bin(), BN_bin2bn(), BN_print_fp(), and BN_print() functions are available in all versions of SSLeay and OpenSSL.

The BN_bn2hex(), BN_bn2dec(), BN_hex2bn(), BN_dec2bn(), BN_bn2mpi(), and BN_mpi2bn() functions were added in SSLeay 0.9.0.

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