pbkdf1_ms.go

package pbkdf1_ms

import (
	"crypto/sha1"
	"strconv"
)

// Key implements C# PasswordDeriveBytes
func Key(password, salt []byte, iterations int, dkLen int) []byte {

	// Prepare base hash
	base := append(password, salt...)

	// Process derivation through iteration count
	for i := 0; i < iterations-1; i++ {
		h := sha1.Sum(base[:])
		base = h[:]
	}
	last := sha1.Sum(base[:])

	// Finalize hash
	out := last[:]

	// Process tailing bytes
	counter := 1
	var extra []byte

	// If ouput is smaller than expected derived key length
	for len(out) < dkLen {
		// Concat counter
		extra = strconv.AppendInt(extra, int64(counter), 10)
		// Concat base hash
		extra = append(extra, base[:]...)
		// Sum it
		extraHash := sha1.Sum(extra)
		// Append to output
		out = append(out, extraHash[:]...)
		// Increment counter
		counter++
	}

	// Return result
	return out[:dkLen]
}