## table of contents

BN_BN2BIN(3SSL) | OpenSSL | BN_BN2BIN(3SSL) |

# 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 ****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 **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 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 2000-2018 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>.

2018-11-28 | 1.1.0j |