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

#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);

*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.

*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).

*bn*(3),

*ERR_get_error*(3),

*BN_zero*(3),

*ASN1_INTEGER_to_BN*(3),

*BN_num_bytes*(3)

Copyright 2000-2016 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>.