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# 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 zeroes 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_bin2lbn()*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 **

**bn**. If *

**bn**is NULL, a new

**BIGNUM**is created. If

**bn**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

**BIGNUM**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 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 the length of valid representation in hexadecimal or decimal digits, and 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 2000-2017 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>.2017-05-25 | 1.1.0f |