# 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.

# 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 BIGNUMs 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.

# 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.