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| author | cvs2svn <admin@example.com> | 2012-07-13 17:49:56 +0000 |
|---|---|---|
| committer | cvs2svn <admin@example.com> | 2012-07-13 17:49:56 +0000 |
| commit | ee04221ea8063435416c7e6369e6eae76843aa71 (patch) | |
| tree | 821921a1dd0a5a3cece91121e121cc63c4b68128 /src/lib/libcrypto/doc/EVP_BytesToKey.pod | |
| parent | adf6731f6e1d04718aee00cb93435143046aee9a (diff) | |
| download | openbsd-eric_g2k12.tar.gz openbsd-eric_g2k12.tar.bz2 openbsd-eric_g2k12.zip | |
This commit was manufactured by cvs2git to create tag 'eric_g2k12'.eric_g2k12
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| -rw-r--r-- | src/lib/libcrypto/doc/EVP_BytesToKey.pod | 67 |
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diff --git a/src/lib/libcrypto/doc/EVP_BytesToKey.pod b/src/lib/libcrypto/doc/EVP_BytesToKey.pod deleted file mode 100644 index d375c46e03..0000000000 --- a/src/lib/libcrypto/doc/EVP_BytesToKey.pod +++ /dev/null | |||
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| 1 | =pod | ||
| 2 | |||
| 3 | =head1 NAME | ||
| 4 | |||
| 5 | EVP_BytesToKey - password based encryption routine | ||
| 6 | |||
| 7 | =head1 SYNOPSIS | ||
| 8 | |||
| 9 | #include <openssl/evp.h> | ||
| 10 | |||
| 11 | int EVP_BytesToKey(const EVP_CIPHER *type,const EVP_MD *md, | ||
| 12 | const unsigned char *salt, | ||
| 13 | const unsigned char *data, int datal, int count, | ||
| 14 | unsigned char *key,unsigned char *iv); | ||
| 15 | |||
| 16 | =head1 DESCRIPTION | ||
| 17 | |||
| 18 | EVP_BytesToKey() derives a key and IV from various parameters. B<type> is | ||
| 19 | the cipher to derive the key and IV for. B<md> is the message digest to use. | ||
| 20 | The B<salt> paramter is used as a salt in the derivation: it should point to | ||
| 21 | an 8 byte buffer or NULL if no salt is used. B<data> is a buffer containing | ||
| 22 | B<datal> bytes which is used to derive the keying data. B<count> is the | ||
| 23 | iteration count to use. The derived key and IV will be written to B<key> | ||
| 24 | and B<iv> respectively. | ||
| 25 | |||
| 26 | =head1 NOTES | ||
| 27 | |||
| 28 | A typical application of this function is to derive keying material for an | ||
| 29 | encryption algorithm from a password in the B<data> parameter. | ||
| 30 | |||
| 31 | Increasing the B<count> parameter slows down the algorithm which makes it | ||
| 32 | harder for an attacker to peform a brute force attack using a large number | ||
| 33 | of candidate passwords. | ||
| 34 | |||
| 35 | If the total key and IV length is less than the digest length and | ||
| 36 | B<MD5> is used then the derivation algorithm is compatible with PKCS#5 v1.5 | ||
| 37 | otherwise a non standard extension is used to derive the extra data. | ||
| 38 | |||
| 39 | Newer applications should use more standard algorithms such as PKCS#5 | ||
| 40 | v2.0 for key derivation. | ||
| 41 | |||
| 42 | =head1 KEY DERIVATION ALGORITHM | ||
| 43 | |||
| 44 | The key and IV is derived by concatenating D_1, D_2, etc until | ||
| 45 | enough data is available for the key and IV. D_i is defined as: | ||
| 46 | |||
| 47 | D_i = HASH^count(D_(i-1) || data || salt) | ||
| 48 | |||
| 49 | where || denotes concatentaion, D_0 is empty, HASH is the digest | ||
| 50 | algorithm in use, HASH^1(data) is simply HASH(data), HASH^2(data) | ||
| 51 | is HASH(HASH(data)) and so on. | ||
| 52 | |||
| 53 | The initial bytes are used for the key and the subsequent bytes for | ||
| 54 | the IV. | ||
| 55 | |||
| 56 | =head1 RETURN VALUES | ||
| 57 | |||
| 58 | EVP_BytesToKey() returns the size of the derived key in bytes. | ||
| 59 | |||
| 60 | =head1 SEE ALSO | ||
| 61 | |||
| 62 | L<evp(3)|evp(3)>, L<rand(3)|rand(3)>, | ||
| 63 | L<EVP_EncryptInit(3)|EVP_EncryptInit(3)> | ||
| 64 | |||
| 65 | =head1 HISTORY | ||
| 66 | |||
| 67 | =cut | ||
