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1 | .Dd $Mdocdate: February 23 2015 $ | ||
2 | .Dt BN_RAND 3 | ||
3 | .Os | ||
4 | .Sh NAME | ||
5 | .Nm BN_rand , | ||
6 | .Nm BN_pseudo_rand , | ||
7 | .Nm BN_rand_range , | ||
8 | .Nm BN_pseudo_rand_range | ||
9 | .Nd generate pseudo-random number | ||
10 | .Sh SYNOPSIS | ||
11 | .In openssl/bn.h | ||
12 | .Ft int | ||
13 | .Fo BN_rand | ||
14 | .Fa "BIGNUM *rnd" | ||
15 | .Fa "int bits" | ||
16 | .Fa "int top" | ||
17 | .Fa "int bottom" | ||
18 | .Fc | ||
19 | .Ft int | ||
20 | .Fo BN_pseudo_rand | ||
21 | .Fa "BIGNUM *rnd" | ||
22 | .Fa "int bits" | ||
23 | .Fa "int top" | ||
24 | .Fa "int bottom" | ||
25 | .Fc | ||
26 | .Ft int | ||
27 | .Fo BN_rand_range | ||
28 | .Fa "BIGNUM *rnd" | ||
29 | .Fa "BIGNUM *range" | ||
30 | .Fc | ||
31 | .Ft int | ||
32 | .Fo BN_pseudo_rand_range | ||
33 | .Fa "BIGNUM *rnd" | ||
34 | .Fa "BIGNUM *range" | ||
35 | .Fc | ||
36 | .Sh DESCRIPTION | ||
37 | .Fn BN_rand | ||
38 | generates a cryptographically strong pseudo-random number of | ||
39 | .Fa bits | ||
40 | bits in length and stores it in | ||
41 | .Fa rnd . | ||
42 | If | ||
43 | .Fa top | ||
44 | is -1, the most significant bit of the random number can be zero. | ||
45 | If | ||
46 | .Fa top | ||
47 | is 0, it is set to 1, and if | ||
48 | .Fa top | ||
49 | is 1, the two most significant bits of the number will be set to 1, so | ||
50 | that the product of two such random numbers will always have | ||
51 | .Pf 2* Fa bits | ||
52 | length. | ||
53 | If | ||
54 | .Fa bottom | ||
55 | is true, the number will be odd. | ||
56 | .Pp | ||
57 | .Fn BN_pseudo_rand | ||
58 | does the same, but pseudo-random numbers generated by this function are | ||
59 | not necessarily unpredictable. | ||
60 | They can be used for non-cryptographic purposes and for certain purposes | ||
61 | in cryptographic protocols, but usually not for key generation etc. | ||
62 | .Pp | ||
63 | .Fn BN_rand_range | ||
64 | generates a cryptographically strong pseudo-random number | ||
65 | .Fa rnd | ||
66 | in the range 0 <= | ||
67 | .Fa rnd No < Fa range . | ||
68 | .Fn BN_pseudo_rand_range | ||
69 | does the same, but is based on | ||
70 | .Fn BN_pseudo_rand , | ||
71 | and hence numbers generated by it are not necessarily unpredictable. | ||
72 | .Sh RETURN VALUES | ||
73 | The functions return 1 on success, 0 on error. | ||
74 | The error codes can be obtained by | ||
75 | .Xr ERR_get_error 3 . | ||
76 | .Sh SEE ALSO | ||
77 | .Xr bn 3 , | ||
78 | .Xr ERR_get_error 3 , | ||
79 | .Xr rand 3 , | ||
80 | .Xr RAND_add 3 , | ||
81 | .Xr RAND_bytes 3 | ||
82 | .Sh HISTORY | ||
83 | .Fn BN_rand | ||
84 | is available in all versions of SSLeay and OpenSSL. | ||
85 | .Fn BN_pseudo_rand | ||
86 | was added in OpenSSL 0.9.5. | ||
87 | The | ||
88 | .Fa top | ||
89 | == -1 case and the function | ||
90 | .Fn BN_rand_range | ||
91 | were added in OpenSSL 0.9.6a. | ||
92 | .Fn BN_pseudo_rand_range | ||
93 | was added in OpenSSL 0.9.6c. | ||