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- .IX Title "BN_bn2bin 3"
- .TH BN_bn2bin 3 "2019-09-12" "1.0.2g" "OpenSSL"
- .\" For nroff, turn off justification. Always turn off hyphenation; it makes
- .\" way too many mistakes in technical documents.
- .if n .ad l
- .nh
- .SH "NAME"
- BN_bn2bin, BN_bin2bn, BN_bn2hex, BN_bn2dec, BN_hex2bn, BN_dec2bn,
- BN_print, BN_print_fp, BN_bn2mpi, BN_mpi2bn \- format conversions
- .SH "SYNOPSIS"
- .IX Header "SYNOPSIS"
- .Vb 1
- \& #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);
- .Ve
- .SH "DESCRIPTION"
- .IX Header "DESCRIPTION"
- \&\fIBN_bn2bin()\fR converts the absolute value of \fBa\fR into big-endian form
- and stores it at \fBto\fR. \fBto\fR must point to BN_num_bytes(\fBa\fR) bytes of
- memory.
- .PP
- \&\fIBN_bin2bn()\fR converts the positive integer in big-endian form of length
- \&\fBlen\fR at \fBs\fR into a \fB\s-1BIGNUM\s0\fR and places it in \fBret\fR. If \fBret\fR is
- \&\s-1NULL,\s0 a new \fB\s-1BIGNUM\s0\fR is created.
- .PP
- \&\fIBN_bn2hex()\fR and \fIBN_bn2dec()\fR return printable strings containing the
- hexadecimal and decimal encoding of \fBa\fR respectively. For negative
- numbers, the string is prefaced with a leading '\-'. The string must be
- freed later using \fIOPENSSL_free()\fR.
- .PP
- \&\fIBN_hex2bn()\fR converts the string \fBstr\fR containing a hexadecimal number
- to a \fB\s-1BIGNUM\s0\fR and stores it in **\fBbn\fR. If *\fBbn\fR is \s-1NULL,\s0 a new
- \&\fB\s-1BIGNUM\s0\fR is created. If \fBbn\fR is \s-1NULL,\s0 it only computes the number's
- length in hexadecimal digits. If the string starts with '\-', the
- number is negative. \fIBN_dec2bn()\fR is the same using the decimal system.
- .PP
- \&\fIBN_print()\fR and \fIBN_print_fp()\fR write the hexadecimal encoding of \fBa\fR,
- with a leading '\-' for negative numbers, to the \fB\s-1BIO\s0\fR or \fB\s-1FILE\s0\fR
- \&\fBfp\fR.
- .PP
- \&\fIBN_bn2mpi()\fR and \fIBN_mpi2bn()\fR convert \fB\s-1BIGNUM\s0\fRs 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 \s-1MSB\s0 set is prefixed with null byte).
- .PP
- \&\fIBN_bn2mpi()\fR stores the representation of \fBa\fR at \fBto\fR, where \fBto\fR
- must be large enough to hold the result. The size can be determined by
- calling BN_bn2mpi(\fBa\fR, \s-1NULL\s0).
- .PP
- \&\fIBN_mpi2bn()\fR converts the \fBlen\fR bytes long representation at \fBs\fR to
- a \fB\s-1BIGNUM\s0\fR and stores it at \fBret\fR, or in a newly allocated \fB\s-1BIGNUM\s0\fR
- if \fBret\fR is \s-1NULL.\s0
- .SH "RETURN VALUES"
- .IX Header "RETURN VALUES"
- \&\fIBN_bn2bin()\fR returns the length of the big-endian number placed at \fBto\fR.
- \&\fIBN_bin2bn()\fR returns the \fB\s-1BIGNUM\s0\fR, \s-1NULL\s0 on error.
- .PP
- \&\fIBN_bn2hex()\fR and \fIBN_bn2dec()\fR return a null-terminated string, or \s-1NULL\s0
- on error. \fIBN_hex2bn()\fR and \fIBN_dec2bn()\fR return the number's length in
- hexadecimal or decimal digits, and 0 on error.
- .PP
- \&\fIBN_print_fp()\fR and \fIBN_print()\fR return 1 on success, 0 on write errors.
- .PP
- \&\fIBN_bn2mpi()\fR returns the length of the representation. \fIBN_mpi2bn()\fR
- returns the \fB\s-1BIGNUM\s0\fR, and \s-1NULL\s0 on error.
- .PP
- The error codes can be obtained by \fIERR_get_error\fR\|(3).
- .SH "SEE ALSO"
- .IX Header "SEE ALSO"
- \&\fIbn\fR\|(3), \fIERR_get_error\fR\|(3), \fIBN_zero\fR\|(3),
- \&\fIASN1_INTEGER_to_BN\fR\|(3),
- \&\fIBN_num_bytes\fR\|(3)
- .SH "HISTORY"
- .IX Header "HISTORY"
- \&\fIBN_bn2bin()\fR, \fIBN_bin2bn()\fR, \fIBN_print_fp()\fR and \fIBN_print()\fR are available
- in all versions of SSLeay and OpenSSL.
- .PP
- \&\fIBN_bn2hex()\fR, \fIBN_bn2dec()\fR, \fIBN_hex2bn()\fR, \fIBN_dec2bn()\fR, \fIBN_bn2mpi()\fR and
- \&\fIBN_mpi2bn()\fR were added in SSLeay 0.9.0.
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