# Sortix nightly manual

This manual documents Sortix nightly, a development build that has not been officially released. You can instead view this document in the latest official manual.

BN_BN2BIN(3) | Library Functions Manual | BN_BN2BIN(3) |

# NAME

`BN_bn2bin`

,
`BN_bn2binpad`

,
`BN_bin2bn`

,
`BN_bn2lebinpad`

,
`BN_lebin2bn`

,
`BN_bn2hex`

,
`BN_bn2dec`

,
`BN_hex2bn`

,
`BN_dec2bn`

,
`BN_asc2bn`

,
`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 **ap`,

`const char *str`);

`int`

`BN_dec2bn`

(`BIGNUM **ap`,

`const char *str`);

`int`

`BN_asc2bn`

(`BIGNUM **ap`,

`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
*`to`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 minus sign. The string must be freed later using free(3).

`BN_hex2bn`

() interprets
`str`as a hexadecimal number. The string may start with a minus sign (‘-’). Conversion stops at the first byte that is not a hexadecimal digit. The number is converted to a

`BIGNUM`and stored in **

`ap`. If *

`ap`is

`NULL`

, a new
`BIGNUM`is created. If

`ap`is

`NULL`

, it only computes the number's length
in hexadecimal digits, also counting the leading minus sign if there is one. A
"negative zero" is converted to zero.
`BN_dec2bn`

() is the same using the decimal
system. `BN_asc2bn`

() infers the number base
from an optional prefix. If `str`starts with “0x” or “0X”, it calls

`BN_hex2bn`

(), otherwise
`BN_dec2bn`

(). If the number is negative, the
minus sign can be given before or after the prefix.
`BN_print`

() and
`BN_print_fp`

() write the hexadecimal
encoding of `a`, with a leading minus sign 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 a NUL 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_bn2binpad`

() and
`BN_bn2lebinpad`

() return the number of bytes
written or -1 if the supplied buffer is too small.
`BN_bin2bn`

() and
`BN_lebin2bn`

() return the
`BIGNUM`, or

`NULL`

on error.
`BN_bn2hex`

() and
`BN_bn2dec`

() return a NUL-terminated string,
or `NULL`

on error.
`BN_hex2bn`

() and
`BN_dec2bn`

() return the number's length in
hexadecimal or decimal digits, also counting the leading minus sign if there
is one, or 0 on error, in which case no new
`BIGNUM`is created.

`BN_asc2bn`

() returns 1 on success or 0 on
error, in which case no new `BIGNUM`is 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`, or

`NULL`

on error.
The error codes can be obtained by
ERR_get_error(3).
# SEE ALSO

ASN1_bn_print(3), ASN1_INTEGER_to_BN(3), BN_new(3), BN_num_bytes(3), BN_zero(3)# HISTORY

`BN_bn2bin`

(),
`BN_bin2bn`

(), and
`BN_print`

() first appeared in SSLeay 0.5.1.
`BN_print_fp`

() first appeared in SSLeay
0.6.0. `BN_bn2hex`

(),
`BN_bn2dec`

(),
`BN_hex2bn`

(),
`BN_dec2bn`

(),
`BN_bn2mpi`

(), and
`BN_mpi2bn`

() first appeared in SSLeay 0.9.0.
All these functions have been available since OpenBSD
2.4.
`BN_asc2bin`

() first appeared in OpenSSL 1.0.0
and has been available since OpenBSD 4.9.
`BN_bn2binpad`

(),
`BN_bn2lebinpad`

(), and
`BN_lebin2bn`

() first appeared in OpenSSL
1.1.0 and have been available since OpenBSD 7.0.December 8, 2021 | Debian |