// Copyright 2011 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package rand import ( "io" "math/big" "os" ) // Prime returns a number, p, of the given size, such that p is prime // with high probability. func Prime(rand io.Reader, bits int) (p *big.Int, err error) { if bits < 1 { err = os.EINVAL } b := uint(bits % 8) if b == 0 { b = 8 } bytes := make([]byte, (bits+7)/8) p = new(big.Int) for { _, err = io.ReadFull(rand, bytes) if err != nil { return nil, err } // Clear bits in the first byte to make sure the candidate has a size <= bits. bytes[0] &= uint8(int(1<