### BN_mpi2bn (3)

#### Leading comments

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#### NAME

BN_bn2bin, BN_bin2bn, 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); 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_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_bin2bn()* converts the positive integer in big-endian form of length
**len** at **s** into a

**BIGNUM**

**ret**. If

**ret**is

**BIGNUM**

*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()* converts the string **str** containing a hexadecimal number
to a

**BIGNUM**

**bn**. If *

**bn**is

**BIGNUM**

**bn**is

*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**

**FILE**

**fp**.

*BN_bn2mpi()* and *BN_mpi2bn()* convert

**BIGNUM**

*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**,

*BN_mpi2bn()* converts the **len** bytes long representation at **s** to
a

**BIGNUM**

**ret**, or in a newly allocated

**BIGNUM**

**ret**is

#### RETURN VALUES

*BN_bn2bin()*returns the length of the big-endian number placed at

**to**.

*BN_bin2bn()*returns the

**BIGNUM**

*BN_bn2hex()* and *BN_bn2dec()* return a null-terminated string, or

*BN_hex2bn()*and

*BN_dec2bn()*return the number's length in hexadecimal or decimal digits, and 0 on error.

*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**

The error codes can be obtained by *ERR_get_error*(3).

#### SEE ALSO

*bn*(3),

*ERR_get_error*(3),

*BN_zero*(3),

*ASN1_INTEGER_to_BN*(3),

*BN_num_bytes*(3)

#### HISTORY

*BN_bn2bin()*,

*BN_bin2bn()*,

*BN_print_fp()*and

*BN_print()*are available in all versions of SSLeay and OpenSSL.

*BN_bn2hex()*, *BN_bn2dec()*, *BN_hex2bn()*, *BN_dec2bn()*, *BN_bn2mpi()* and
*BN_mpi2bn()* were added in SSLeay 0.9.0.