f4401cd869
alter des.h to be friendly with openssl/des.h (you can include both in the same file) make libkrb to depend on libdes. bump major. massage various portioin of heimdal to be friendly with openssl 0.9.7b.
209 lines
6.3 KiB
Groff
209 lines
6.3 KiB
Groff
.\" $NetBSD: EVP_BytesToKey.3,v 1.1 2003/07/24 14:16:40 itojun Exp $
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.\" ======================================================================
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.\"
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.IX Title "EVP_BytesToKey 3"
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.TH EVP_BytesToKey 3 "0.9.7b" "2001-12-03" "OpenSSL"
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.UC
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.SH "NAME"
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.Vb 1
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\& EVP_BytesToKey - password based encryption routine
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.Ve
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.SH "LIBRARY"
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libcrypto, -lcrypto
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.SH "SYNOPSIS"
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.IX Header "SYNOPSIS"
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.Vb 1
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\& #include <openssl/evp.h>
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.Ve
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.Vb 4
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\& int EVP_BytesToKey(const EVP_CIPHER *type,const EVP_MD *md,
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\& const unsigned char *salt,
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\& const unsigned char *data, int datal, int count,
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\& unsigned char *key,unsigned char *iv);
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.Ve
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.SH "DESCRIPTION"
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.IX Header "DESCRIPTION"
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\&\fIEVP_BytesToKey()\fR derives a key and \s-1IV\s0 from various parameters. \fBtype\fR is
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the cipher to derive the key and \s-1IV\s0 for. \fBmd\fR is the message digest to use.
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The \fBsalt\fR paramter is used as a salt in the derivation: it should point to
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an 8 byte buffer or \s-1NULL\s0 if no salt is used. \fBdata\fR is a buffer containing
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\&\fBdatal\fR bytes which is used to derive the keying data. \fBcount\fR is the
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iteration count to use. The derived key and \s-1IV\s0 will be written to \fBkey\fR
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and \fBiv\fR respectively.
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.SH "NOTES"
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.IX Header "NOTES"
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A typical application of this function is to derive keying material for an
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encryption algorithm from a password in the \fBdata\fR parameter.
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.PP
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Increasing the \fBcount\fR parameter slows down the algorithm which makes it
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harder for an attacker to peform a brute force attack using a large number
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of candidate passwords.
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.PP
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If the total key and \s-1IV\s0 length is less than the digest length and
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\&\fB\s-1MD5\s0\fR is used then the derivation algorithm is compatible with PKCS#5 v1.5
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otherwise a non standard extension is used to derive the extra data.
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.PP
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Newer applications should use more standard algorithms such as PKCS#5
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v2.0 for key derivation.
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.SH "KEY DERIVATION ALGORITHM"
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.IX Header "KEY DERIVATION ALGORITHM"
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The key and \s-1IV\s0 is derived by concatenating D_1, D_2, etc until
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enough data is available for the key and \s-1IV\s0. D_i is defined as:
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.PP
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.Vb 1
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\& D_i = HASH^count(D_(i-1) || data || salt)
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.Ve
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where || denotes concatentaion, D_0 is empty, \s-1HASH\s0 is the digest
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algorithm in use, HASH^1(data) is simply HASH(data), HASH^2(data)
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is HASH(HASH(data)) and so on.
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.PP
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The initial bytes are used for the key and the subsequent bytes for
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the \s-1IV\s0.
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.SH "RETURN VALUES"
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.IX Header "RETURN VALUES"
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\&\fIEVP_BytesToKey()\fR returns the size of the derived key in bytes.
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.SH "SEE ALSO"
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.IX Header "SEE ALSO"
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openssl_evp(3), openssl_rand(3),
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EVP_EncryptInit(3),
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.SH "HISTORY"
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.IX Header "HISTORY"
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