// Reseed uses the current generator state and the given seed value to
// update the generator state. Care is taken to make sure that
// knowledge of the new state after a reseed does not allow to
// reconstruct previous output values of the generator.
//
// This is like the ReseedInt64() method, but the seed is given as a
// byte slice instead of as an int64.
func (gen *Generator) Reseed(seed []byte) {
hash := sha256d.New()
hash.Write(gen.key)
hash.Write(seed)
gen.setKey(hash.Sum(nil))
gen.inc()
trace.T("fortuna/generator", trace.PrioVerbose, "seed updated")
}
// NewAccumulator allocates a new instance of the Fortuna random
// number generator. The argument 'newCipher' allows to choose a
// block cipher like Serpent or Twofish instead of the default AES.
// NewAccumulator(aes.NewCipher, seedFileName) is the same as
// NewRNG(seedFileName). See the documentation for NewRNG() for more
// information.
func NewAccumulator(newCipher NewCipher, seedFileName string) (*Accumulator, error) {
acc := &Accumulator{
gen: NewGenerator(newCipher),
}
for i := 0; i < len(acc.pool); i++ {
acc.pool[i] = sha256d.New()
}
acc.stopSources = make(chan bool)
if seedFileName != "" {
seedFile, err := os.OpenFile(seedFileName,
os.O_RDWR|os.O_CREATE|os.O_SYNC, os.FileMode(0600))
if err != nil {
return nil, err
}
acc.seedFile = seedFile
err = flock(acc.seedFile)
if err != nil {
acc.seedFile.Close()
return nil, err
}
// The initial seed of the generator depends on the current
// time. This (partially) protects us against old seed files
// being restored from backups, etc.
err = acc.updateSeedFile()
if err != nil {
acc.seedFile.Close()
return nil, err
}
quit := make(chan bool)
acc.stopAutoSave = quit
go func() {
ticker := time.Tick(seedFileUpdateInterval)
for {
select {
case <-quit:
return
case <-ticker:
acc.writeSeedFile()
}
}
}()
}
return acc, nil
}
