/src/botan/src/lib/math/bigint/big_rand.cpp
Line | Count | Source (jump to first uncovered line) |
1 | | /* |
2 | | * BigInt Random Generation |
3 | | * (C) 1999-2007 Jack Lloyd |
4 | | * |
5 | | * Botan is released under the Simplified BSD License (see license.txt) |
6 | | */ |
7 | | |
8 | | #include <botan/bigint.h> |
9 | | #include <botan/rng.h> |
10 | | #include <botan/internal/rounding.h> |
11 | | |
12 | | namespace Botan { |
13 | | |
14 | | /* |
15 | | * Randomize this number |
16 | | */ |
17 | | void BigInt::randomize(RandomNumberGenerator& rng, |
18 | | size_t bitsize, bool set_high_bit) |
19 | 515k | { |
20 | 515k | set_sign(Positive); |
21 | | |
22 | 515k | if(bitsize == 0) |
23 | 0 | { |
24 | 0 | clear(); |
25 | 0 | } |
26 | 515k | else |
27 | 515k | { |
28 | 515k | secure_vector<uint8_t> array = rng.random_vec(round_up(bitsize, 8) / 8); |
29 | | |
30 | | // Always cut unwanted bits |
31 | 515k | if(bitsize % 8) |
32 | 289k | array[0] &= 0xFF >> (8 - (bitsize % 8)); |
33 | | |
34 | | // Set the highest bit if wanted |
35 | 515k | if (set_high_bit) |
36 | 37.3k | array[0] |= 0x80 >> ((bitsize % 8) ? (8 - bitsize % 8) : 0); |
37 | | |
38 | 515k | binary_decode(array); |
39 | 515k | } |
40 | 515k | } |
41 | | |
42 | | /* |
43 | | * Generate a random integer within given range |
44 | | */ |
45 | | BigInt BigInt::random_integer(RandomNumberGenerator& rng, |
46 | | const BigInt& min, const BigInt& max) |
47 | 89.0k | { |
48 | 89.0k | if(min.is_negative() || max.is_negative() || max <= min) |
49 | 0 | throw Invalid_Argument("BigInt::random_integer invalid range"); |
50 | | |
51 | 89.0k | BigInt r; |
52 | | |
53 | 89.0k | const size_t bits = max.bits(); |
54 | | |
55 | 89.0k | do |
56 | 103k | { |
57 | 103k | r.randomize(rng, bits, false); |
58 | 103k | } |
59 | 103k | while(r < min || r >= max); |
60 | | |
61 | 89.0k | return r; |
62 | 89.0k | } |
63 | | |
64 | | } |