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RAND.go
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RAND.go
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/*
* Copyright (c) 2012-2020 MIRACL UK Ltd.
*
* This file is part of MIRACL Core
* (see https://github.com/miracl/core).
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* Cryptographic strong random number generator
*
* Unguessable seed -> SHA -> PRNG internal state -> SHA -> random numbers
* Slow - but secure
*
* See ftp://ftp.rsasecurity.com/pub/pdfs/bull-1.pdf for a justification
*/
/* Marsaglia & Zaman Random number generator constants */
package core
//import "fmt"
const rand_NK int = 21
const rand_NJ int = 6
const rand_NV int = 8
type RAND struct {
ira [rand_NK]uint32 /* random number... */
rndptr int
borrow uint32
pool_ptr int
pool [32]byte
}
/* Terminate and clean up */
func (R *RAND) Clean() { /* kill internal state */
R.pool_ptr = 0
R.rndptr = 0
for i := 0; i < 32; i++ {
R.pool[i] = 0
}
for i := 0; i < rand_NK; i++ {
R.ira[i] = 0
}
R.borrow = 0
}
func NewRAND() *RAND {
R := new(RAND)
R.Clean()
return R
}
func (R *RAND) sbrand() uint32 { /* Marsaglia & Zaman random number generator */
R.rndptr++
if R.rndptr < rand_NK {
return R.ira[R.rndptr]
}
R.rndptr = 0
k := rand_NK - rand_NJ
for i := 0; i < rand_NK; i++ { /* calculate next NK values */
if k == rand_NK {
k = 0
}
t := R.ira[k]
pdiff := t - R.ira[i] - R.borrow
if pdiff < t {
R.borrow = 0
}
if pdiff > t {
R.borrow = 1
}
R.ira[i] = pdiff
k++
}
return R.ira[0]
}
func (R *RAND) sirand(seed uint32) {
var m uint32 = 1
R.borrow = 0
R.rndptr = 0
R.ira[0] ^= seed
for i := 1; i < rand_NK; i++ { /* fill initialisation vector */
in := (rand_NV * i) % rand_NK
R.ira[in] ^= m /* note XOR */
t := m
m = seed - m
seed = t
}
for i := 0; i < 10000; i++ {
R.sbrand()
} /* "warm-up" & stir the generator */
}
func (R *RAND) fill_pool() {
sh := NewHASH256()
for i := 0; i < 128; i++ {
sh.Process(byte(R.sbrand() & 0xff))
}
W := sh.Hash()
for i := 0; i < 32; i++ {
R.pool[i] = W[i]
}
R.pool_ptr = 0
}
func pack(b [4]byte) uint32 { /* pack 4 bytes into a 32-bit Word */
return (((uint32(b[3])) & 0xff) << 24) | ((uint32(b[2]) & 0xff) << 16) | ((uint32(b[1]) & 0xff) << 8) | (uint32(b[0]) & 0xff)
}
/* Initialize RNG with some real entropy from some external source */
func (R *RAND) Seed(rawlen int, raw []byte) { /* initialise from at least 128 byte string of raw random entropy */
var b [4]byte
sh := NewHASH256()
R.pool_ptr = 0
for i := 0; i < rand_NK; i++ {
R.ira[i] = 0
}
if rawlen > 0 {
for i := 0; i < rawlen; i++ {
sh.Process(raw[i])
}
digest := sh.Hash()
/* initialise PRNG from distilled randomness */
for i := 0; i < 8; i++ {
b[0] = digest[4*i]
b[1] = digest[4*i+1]
b[2] = digest[4*i+2]
b[3] = digest[4*i+3]
R.sirand(pack(b))
}
}
R.fill_pool()
}
/* get random byte */
func (R *RAND) GetByte() byte {
r := R.pool[R.pool_ptr]
R.pool_ptr++
if R.pool_ptr >= 32 {
R.fill_pool()
}
return byte(r & 0xff)
}
/* test main program */
/*
func main() {
var raw [100]byte
rng:=NewRAND()
rng.Clean()
for i:=0;i<100;i++ {raw[i]=byte(i)}
rng.Seed(100,raw[:])
for i:=0;i<1000;i++ {
fmt.Printf("%03d ",rng.GetByte())
}
}
*/