X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/blobdiff_plain/c504615937cc17b50794b534f4305851ea03cbae..a561f9ff0e82fe5b39428c7d9da4d16df3bb0440:/secure/lib/libcrypto/man/BN_num_bytes.3

diff --git a/secure/lib/libcrypto/man/BN_num_bytes.3 b/secure/lib/libcrypto/man/BN_num_bytes.3
index af3af6f0c9..4c780f5527 100644
--- a/secure/lib/libcrypto/man/BN_num_bytes.3
+++ b/secure/lib/libcrypto/man/BN_num_bytes.3
@@ -1,8 +1,7 @@
-.\" Automatically generated by Pod::Man version 1.15
-.\" Wed Feb 19 16:42:48 2003
+.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.14
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+.\" ========================================================================
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-.\" ======================================================================
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 .IX Title "BN_num_bytes 3"
-.TH BN_num_bytes 3 "0.9.7a" "2003-02-19" "OpenSSL"
-.UC
+.TH BN_num_bytes 3 "2005-07-06" "0.9.8" "OpenSSL"
 .SH "NAME"
-BN_num_bits, BN_num_bytes, BN_num_bits_word \- get \s-1BIGNUM\s0 size
+BN_num_bits, BN_num_bytes, BN_num_bits_word \- get BIGNUM size
 .SH "SYNOPSIS"
 .IX Header "SYNOPSIS"
 .Vb 1
 \& #include <openssl/bn.h>
 .Ve
+.PP
 .Vb 1
 \& int BN_num_bytes(const BIGNUM *a);
 .Ve
+.PP
 .Vb 1
 \& int BN_num_bits(const BIGNUM *a);
 .Ve
+.PP
 .Vb 1
 \& int BN_num_bits_word(BN_ULONG w);
 .Ve
 .SH "DESCRIPTION"
 .IX Header "DESCRIPTION"
-These functions return the size of a \fB\s-1BIGNUM\s0\fR in bytes or bits,
-and the size of an unsigned integer in bits.
+\&\fIBN_num_bytes()\fR returns the size of a \fB\s-1BIGNUM\s0\fR in bytes.
+.PP
+\&\fIBN_num_bits_word()\fR returns the number of significant bits in a word.
+If we take 0x00000432 as an example, it returns 11, not 16, not 32.
+Basically, except for a zero, it returns \fIfloor(log2(w))+1\fR.
+.PP
+\&\fIBN_num_bits()\fR returns the number of significant bits in a \fB\s-1BIGNUM\s0\fR,
+following the same principle as \fIBN_num_bits_word()\fR.
 .PP
 \&\fIBN_num_bytes()\fR is a macro.
 .SH "RETURN VALUES"
 .IX Header "RETURN VALUES"
 The size.
+.SH "NOTES"
+.IX Header "NOTES"
+Some have tried using \fIBN_num_bits()\fR on individual numbers in \s-1RSA\s0 keys,
+\&\s-1DH\s0 keys and \s-1DSA\s0 keys, and found that they don't always come up with
+the number of bits they expected (something like 512, 1024, 2048,
+\&...).  This is because generating a number with some specific number
+of bits doesn't always set the highest bits, thereby making the number
+of \fIsignificant\fR bits a little lower.  If you want to know the \*(L"key
+size\*(R" of such a key, either use functions like \fIRSA_size()\fR, \fIDH_size()\fR
+and \fIDSA_size()\fR, or use \fIBN_num_bytes()\fR and multiply with 8 (although
+there's no real guarantee that will match the \*(L"key size\*(R", just a lot
+more probability).
 .SH "SEE ALSO"
 .IX Header "SEE ALSO"
-bn(3)
+\&\fIbn\fR\|(3), \fIDH_size\fR\|(3), \fIDSA_size\fR\|(3),
+\&\fIRSA_size\fR\|(3)
 .SH "HISTORY"
 .IX Header "HISTORY"
 \&\fIBN_num_bytes()\fR, \fIBN_num_bits()\fR and \fIBN_num_bits_word()\fR are available in