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Diffstat (limited to 'botan/src/math/bigint/big_rand.cpp')
-rw-r--r-- | botan/src/math/bigint/big_rand.cpp | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/botan/src/math/bigint/big_rand.cpp b/botan/src/math/bigint/big_rand.cpp new file mode 100644 index 0000000..b641bae --- /dev/null +++ b/botan/src/math/bigint/big_rand.cpp @@ -0,0 +1,61 @@ +/* +* BigInt Random Generation +* (C) 1999-2007 Jack Lloyd +* +* Distributed under the terms of the Botan license +*/ + +#include <botan/bigint.h> +#include <botan/parsing.h> + +namespace Botan { + +/* +* Construct a BigInt of a specific form +*/ +BigInt::BigInt(NumberType type, u32bit bits) + { + set_sign(Positive); + + if(type == Power2) + set_bit(bits); + else + throw Invalid_Argument("BigInt(NumberType): Unknown type"); + } + +/* +* Randomize this number +*/ +void BigInt::randomize(RandomNumberGenerator& rng, + u32bit bitsize) + { + set_sign(Positive); + + if(bitsize == 0) + clear(); + else + { + SecureVector<byte> array((bitsize + 7) / 8); + rng.randomize(array, array.size()); + if(bitsize % 8) + array[0] &= 0xFF >> (8 - (bitsize % 8)); + array[0] |= 0x80 >> ((bitsize % 8) ? (8 - bitsize % 8) : 0); + binary_decode(array, array.size()); + } + } + +/* +* Generate a random integer within given range +*/ +BigInt BigInt::random_integer(RandomNumberGenerator& rng, + const BigInt& min, const BigInt& max) + { + BigInt range = max - min; + + if(range <= 0) + throw Invalid_Argument("random_integer: invalid min/max values"); + + return (min + (BigInt(rng, range.bits() + 2) % range)); + } + +} |