/************************************************* * BigInt Random Generation Source File * * (C) 1999-2007 Jack Lloyd * *************************************************/ #include #include #include #include namespace Botan { /************************************************* * Construct a BigInt of a specific form * *************************************************/ BigInt::BigInt(NumberType type, u32bit bits) { set_sign(Positive); if(type == Random && bits) randomize(bits); else if(type == Power2) set_bit(bits); else throw Invalid_Argument("BigInt(NumberType): Unknown type"); } /************************************************* * Randomize this number * *************************************************/ void BigInt::randomize(u32bit bitsize) { set_sign(Positive); if(bitsize == 0) clear(); else { SecureVector array((bitsize + 7) / 8); Global_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 * *************************************************/ BigInt random_integer(u32bit bits) { BigInt x; x.randomize(bits); return x; } /************************************************* * Generate a random integer within given range * *************************************************/ BigInt random_integer(const BigInt& min, const BigInt& max) { BigInt range = max - min; if(range <= 0) throw Invalid_Argument("random_integer: invalid min/max values"); return (min + (random_integer(range.bits() + 2) % range)); } /************************************************* * Generate a random safe prime * *************************************************/ BigInt random_safe_prime(u32bit bits) { if(bits <= 64) throw Invalid_Argument("random_safe_prime: Can't make a prime of " + to_string(bits) + " bits"); BigInt p; do p = (random_prime(bits - 1) << 1) + 1; while(!is_prime(p)); return p; } }