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

`BN_bn2bin`

,
`BN_bin2bn`

, `BN_bn2hex`

,
`BN_bn2dec`

, `BN_hex2bn`

,
`BN_dec2bn`

, `BN_asc2bn`

,
`BN_print`

, `BN_print_fp`

,
`BN_bn2mpi`

, `BN_mpi2bn`

— format conversions

```
#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_asc2bn`

(`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_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_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 *`a`. If
*`a` is `NULL`

, a new
`BIGNUM` is created. If `a` 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`

.

`BN_bn2bin`

() returns the length of the
big-endian number placed at `to`.
`BN_bin2bn`

() returns 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).

`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.

June 10, 2019 | OpenBSD-current |