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author | beck <> | 2000-03-19 11:13:58 +0000 |
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committer | beck <> | 2000-03-19 11:13:58 +0000 |
commit | 796d609550df3a33fc11468741c5d2f6d3df4c11 (patch) | |
tree | 6c6d539061caa20372dad0ac4ddb1dfae2fbe7fe /src/lib/libcrypto/doc/RAND_add.pod | |
parent | 5be3114c1fd7e0dfea1e38d3abb4cbba75244419 (diff) | |
download | openbsd-796d609550df3a33fc11468741c5d2f6d3df4c11.tar.gz openbsd-796d609550df3a33fc11468741c5d2f6d3df4c11.tar.bz2 openbsd-796d609550df3a33fc11468741c5d2f6d3df4c11.zip |
OpenSSL 0.9.5 merge
*warning* this bumps shared lib minors for libssl and libcrypto from 2.1 to 2.2
if you are using the ssl26 packages for ssh and other things to work you will
need to get new ones (see ~beck/libsslsnap/<arch>) on cvs or ~beck/src-patent.tar.gz on cvs
Diffstat (limited to 'src/lib/libcrypto/doc/RAND_add.pod')
-rw-r--r-- | src/lib/libcrypto/doc/RAND_add.pod | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/src/lib/libcrypto/doc/RAND_add.pod b/src/lib/libcrypto/doc/RAND_add.pod new file mode 100644 index 0000000000..0a13ec2a92 --- /dev/null +++ b/src/lib/libcrypto/doc/RAND_add.pod | |||
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1 | =pod | ||
2 | |||
3 | =head1 NAME | ||
4 | |||
5 | RAND_add, RAND_seed, RAND_screen - add entropy to the PRNG | ||
6 | |||
7 | =head1 SYNOPSIS | ||
8 | |||
9 | #include <openssl/rand.h> | ||
10 | |||
11 | void RAND_seed(const void *buf, int num); | ||
12 | |||
13 | void RAND_add(const void *buf, int num, double entropy); | ||
14 | |||
15 | int RAND_status(void); | ||
16 | |||
17 | void RAND_screen(void); | ||
18 | |||
19 | =head1 DESCRIPTION | ||
20 | |||
21 | RAND_add() mixes the B<num> bytes at B<buf> into the PRNG state. Thus, | ||
22 | if the data at B<buf> are unpredictable to an adversary, this | ||
23 | increases the uncertainty about the state and makes the PRNG output | ||
24 | less predictable. Suitable input comes from user interaction (random | ||
25 | key presses, mouse movements) and certain hardware events. The | ||
26 | B<entropy> argument is (the lower bound of) an estimate of how much | ||
27 | randomness is contained in B<buf>, measured in bytes. Details about | ||
28 | sources of randomness and how to estimate their entropy can be found | ||
29 | in the literature, e.g. RFC 1750. | ||
30 | |||
31 | RAND_add() may be called with sensitive data such as user entered | ||
32 | passwords. The seed values cannot be recovered from the PRNG output. | ||
33 | |||
34 | OpenSSL makes sure that the PRNG state is unique for each thread. On | ||
35 | systems that provide C</dev/urandom>, the randomness device is used | ||
36 | to seed the PRNG transparently. However, on all other systems, the | ||
37 | application is responsible for seeding the PRNG by calling RAND_add(), | ||
38 | L<RAND_egd(3)|RAND_egd(3)> | ||
39 | or L<RAND_load_file(3)|RAND_load_file(3)>. | ||
40 | |||
41 | RAND_seed() is equivalent to RAND_add() when B<num == entropy>. | ||
42 | |||
43 | The RAND_screen() function is available for the convenience of Windows | ||
44 | programmers. It adds the current contents of the screen to the PRNG. | ||
45 | For applications that can catch Windows events, seeding the PRNG with | ||
46 | the parameters of B<WM_MOUSEMOVE> events is a significantly better | ||
47 | source of randomness. It should be noted that both methods cannot be | ||
48 | used on servers that run without user interaction. | ||
49 | |||
50 | =head1 RETURN VALUES | ||
51 | |||
52 | RAND_status() returns 1 if the PRNG has been seeded with enough data, | ||
53 | 0 otherwise. | ||
54 | |||
55 | The other functions do not return values. | ||
56 | |||
57 | =head1 SEE ALSO | ||
58 | |||
59 | L<rand(3)|rand(3)>, L<RAND_egd(3)|RAND_egd(3)>, | ||
60 | L<RAND_load_file(3)|RAND_load_file(3)>, L<RAND_cleanup(3)|RAND_cleanup(3)> | ||
61 | |||
62 | =head1 HISTORY | ||
63 | |||
64 | RAND_seed() and RAND_screen() are available in all versions of SSLeay | ||
65 | and OpenSSL. RAND_add() and RAND_status() have been added in OpenSSL | ||
66 | 0.9.5. | ||
67 | |||
68 | =cut | ||