1=pod 2 3=head1 NAME 4 5BN_bn2binpad, 6BN_bn2bin, BN_bin2bn, BN_bn2lebinpad, BN_lebin2bn, BN_bn2hex, BN_bn2dec, 7BN_hex2bn, BN_dec2bn, BN_print, BN_print_fp, BN_bn2mpi, 8BN_mpi2bn - format conversions 9 10=head1 SYNOPSIS 11 12 #include <openssl/bn.h> 13 14 int BN_bn2bin(const BIGNUM *a, unsigned char *to); 15 int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen); 16 BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret); 17 18 int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen); 19 BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret); 20 21 char *BN_bn2hex(const BIGNUM *a); 22 char *BN_bn2dec(const BIGNUM *a); 23 int BN_hex2bn(BIGNUM **a, const char *str); 24 int BN_dec2bn(BIGNUM **a, const char *str); 25 26 int BN_print(BIO *fp, const BIGNUM *a); 27 int BN_print_fp(FILE *fp, const BIGNUM *a); 28 29 int BN_bn2mpi(const BIGNUM *a, unsigned char *to); 30 BIGNUM *BN_mpi2bn(unsigned char *s, int len, BIGNUM *ret); 31 32=head1 DESCRIPTION 33 34BN_bn2bin() converts the absolute value of B<a> into big-endian form 35and stores it at B<to>. B<to> must point to BN_num_bytes(B<a>) bytes of 36memory. 37 38BN_bn2binpad() also converts the absolute value of B<a> into big-endian form 39and stores it at B<to>. B<tolen> indicates the length of the output buffer 40B<to>. The result is padded with zeros if necessary. If B<tolen> is less than 41BN_num_bytes(B<a>) an error is returned. 42 43BN_bin2bn() converts the positive integer in big-endian form of length 44B<len> at B<s> into a B<BIGNUM> and places it in B<ret>. If B<ret> is 45NULL, a new B<BIGNUM> is created. 46 47BN_bn2lebinpad() and BN_lebin2bn() are identical to BN_bn2binpad() and 48BN_bin2bn() except the buffer is in little-endian format. 49 50BN_bn2hex() and BN_bn2dec() return printable strings containing the 51hexadecimal and decimal encoding of B<a> respectively. For negative 52numbers, the string is prefaced with a leading '-'. The string must be 53freed later using OPENSSL_free(). 54 55BN_hex2bn() takes as many characters as possible from the string B<str>, 56including the leading character '-' which means negative, to form a valid 57hexadecimal number representation and converts them to a B<BIGNUM> and 58stores it in **B<a>. If *B<a> is NULL, a new B<BIGNUM> is created. If 59B<a> is NULL, it only computes the length of valid representation. 60A "negative zero" is converted to zero. 61BN_dec2bn() is the same using the decimal system. 62 63BN_print() and BN_print_fp() write the hexadecimal encoding of B<a>, 64with a leading '-' for negative numbers, to the B<BIO> or B<FILE> 65B<fp>. 66 67BN_bn2mpi() and BN_mpi2bn() convert B<BIGNUM>s from and to a format 68that consists of the number's length in bytes represented as a 4-byte 69big-endian number, and the number itself in big-endian format, where 70the most significant bit signals a negative number (the representation 71of numbers with the MSB set is prefixed with null byte). 72 73BN_bn2mpi() stores the representation of B<a> at B<to>, where B<to> 74must be large enough to hold the result. The size can be determined by 75calling BN_bn2mpi(B<a>, NULL). 76 77BN_mpi2bn() converts the B<len> bytes long representation at B<s> to 78a B<BIGNUM> and stores it at B<ret>, or in a newly allocated B<BIGNUM> 79if B<ret> is NULL. 80 81=head1 RETURN VALUES 82 83BN_bn2bin() returns the length of the big-endian number placed at B<to>. 84BN_bin2bn() returns the B<BIGNUM>, NULL on error. 85 86BN_bn2binpad() returns the number of bytes written or -1 if the supplied 87buffer is too small. 88 89BN_bn2hex() and BN_bn2dec() return a null-terminated string, or NULL 90on error. BN_hex2bn() and BN_dec2bn() return the number of characters 91used in parsing, or 0 on error, in which 92case no new B<BIGNUM> will be created. 93 94BN_print_fp() and BN_print() return 1 on success, 0 on write errors. 95 96BN_bn2mpi() returns the length of the representation. BN_mpi2bn() 97returns the B<BIGNUM>, and NULL on error. 98 99The error codes can be obtained by L<ERR_get_error(3)>. 100 101=head1 SEE ALSO 102 103L<ERR_get_error(3)>, L<BN_zero(3)>, 104L<ASN1_INTEGER_to_BN(3)>, 105L<BN_num_bytes(3)> 106 107=head1 COPYRIGHT 108 109Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved. 110 111Licensed under the OpenSSL license (the "License"). You may not use 112this file except in compliance with the License. You can obtain a copy 113in the file LICENSE in the source distribution or at 114L<https://www.openssl.org/source/license.html>. 115 116=cut 117