goext/cryptext/pronouncablePassword.go

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2024-01-14 01:37:38 +01:00
package cryptext
import (
"crypto/rand"
"io"
"math/big"
mathrand "math/rand"
"strings"
)
const (
ppStartChar = "BCDFGHJKLMNPQRSTVWXZ"
ppEndChar = "ABDEFIKMNORSTUXYZ"
ppVowel = "AEIOUY"
ppConsonant = "BCDFGHJKLMNPQRSTVWXZ"
ppSegmentLenMin = 3
ppSegmentLenMax = 7
ppMaxRepeatedVowel = 2
ppMaxRepeatedConsonant = 2
)
var ppContinuation = map[uint8]string{
'A': "BCDFGHJKLMNPRSTVWXYZ",
'B': "ADFIKLMNORSTUY",
'C': "AEIKOUY",
'D': "AEILORSUYZ",
'E': "BCDFGHJKLMNPRSTVWXYZ",
'F': "ADEGIKLOPRTUY",
'G': "ABDEFHILMNORSTUY",
'H': "AEIOUY",
'I': "BCDFGHJKLMNPRSTVWXZ",
'J': "AEIOUY",
'K': "ADEFHILMNORSTUY",
'L': "ADEFGIJKMNOPSTUVWYZ",
'M': "ABEFIKOPSTUY",
'N': "ABEFIKOPSTUY",
'O': "BCDFGHJKLMNPRSTVWXYZ",
'P': "AEFIJLORSTUY",
'Q': "AEIOUY",
'R': "ADEFGHIJKLMNOPSTUVYZ",
'S': "ACDEIKLOPTUYZ",
'T': "AEHIJOPRSUWY",
'U': "BCDFGHJKLMNPRSTVWXZ",
'V': "AEIOUY",
'W': "AEIOUY",
'X': "AEIOUY",
'Y': "ABCDFGHKLMNPRSTVXZ",
'Z': "AEILOTUY",
}
var ppLog2Map = map[int]float64{
1: 0.00000000,
2: 1.00000000,
3: 1.58496250,
4: 2.00000000,
5: 2.32192809,
6: 2.58496250,
7: 2.80735492,
8: 3.00000000,
9: 3.16992500,
10: 3.32192809,
11: 3.45943162,
12: 3.58496250,
13: 3.70043972,
14: 3.80735492,
15: 3.90689060,
16: 4.00000000,
17: 4.08746284,
18: 4.16992500,
19: 4.24792751,
20: 4.32192809,
21: 4.39231742,
22: 4.45943162,
23: 4.52356196,
24: 4.58496250,
25: 4.64385619,
26: 4.70043972,
27: 4.75488750,
28: 4.80735492,
29: 4.85798100,
30: 4.90689060,
31: 4.95419631,
32: 5.00000000,
}
var (
ppVowelMap = ppMakeSet(ppVowel)
ppConsonantMap = ppMakeSet(ppConsonant)
ppEndCharMap = ppMakeSet(ppEndChar)
)
func ppMakeSet(v string) map[uint8]bool {
mp := make(map[uint8]bool, len(v))
for _, chr := range v {
mp[uint8(chr)] = true
}
return mp
}
func ppRandInt(rng io.Reader, max int) int {
v, err := rand.Int(rng, big.NewInt(int64(max)))
if err != nil {
panic(err)
}
return int(v.Int64())
}
func ppRand(rng io.Reader, chars string, entropy *float64) uint8 {
chr := chars[ppRandInt(rng, len(chars))]
*entropy = *entropy + ppLog2Map[len(chars)]
return chr
}
func ppCharType(chr uint8) (bool, bool) {
_, ok1 := ppVowelMap[chr]
_, ok2 := ppConsonantMap[chr]
return ok1, ok2
}
func ppCharsetRemove(cs string, set map[uint8]bool, allowEmpty bool) string {
result := ""
for _, chr := range cs {
if _, ok := set[uint8(chr)]; !ok {
result += string(chr)
}
}
if result == "" && !allowEmpty {
return cs
}
return result
}
func ppCharsetFilter(cs string, set map[uint8]bool, allowEmpty bool) string {
result := ""
for _, chr := range cs {
if _, ok := set[uint8(chr)]; ok {
result += string(chr)
}
}
if result == "" && !allowEmpty {
return cs
}
return result
}
func PronouncablePasswordExt(rng io.Reader, pwlen int) (string, float64) {
// kinda pseudo markov-chain - with a few extra rules and no weights...
if pwlen <= 0 {
return "", 0
}
vowelCount := 0
consoCount := 0
entropy := float64(0)
startChar := ppRand(rng, ppStartChar, &entropy)
result := string(startChar)
currentChar := startChar
isVowel, isConsonant := ppCharType(currentChar)
if isVowel {
vowelCount = 1
}
if isConsonant {
consoCount = ppMaxRepeatedConsonant
}
segmentLen := 1
segmentLenTarget := ppSegmentLenMin + ppRandInt(rng, ppSegmentLenMax-ppSegmentLenMin)
for len(result) < pwlen {
charset := ppContinuation[currentChar]
if vowelCount >= ppMaxRepeatedVowel {
charset = ppCharsetRemove(charset, ppVowelMap, false)
}
if consoCount >= ppMaxRepeatedConsonant {
charset = ppCharsetRemove(charset, ppConsonantMap, false)
}
lastOfSegment := false
newSegment := false
if len(result)+1 == pwlen {
// last of result
charset = ppCharsetFilter(charset, ppEndCharMap, false)
} else if segmentLen+1 == segmentLenTarget {
// last of segment
charsetNew := ppCharsetFilter(charset, ppEndCharMap, true)
if charsetNew != "" {
charset = charsetNew
lastOfSegment = true
}
} else if segmentLen >= segmentLenTarget {
// (perhaps) start of new segment
if _, ok := ppEndCharMap[currentChar]; ok {
charset = ppStartChar
newSegment = true
} else {
// continue segment for one more char to (hopefully) find an end-char
charsetNew := ppCharsetFilter(charset, ppEndCharMap, true)
if charsetNew != "" {
charset = charsetNew
lastOfSegment = true
}
}
} else {
// normal continuation
}
newChar := ppRand(rng, charset, &entropy)
if lastOfSegment {
currentChar = newChar
segmentLen++
result += strings.ToLower(string(newChar))
} else if newSegment {
currentChar = newChar
segmentLen = 1
result += strings.ToUpper(string(newChar))
segmentLenTarget = ppSegmentLenMin + ppRandInt(rng, ppSegmentLenMax-ppSegmentLenMin)
vowelCount = 0
consoCount = 0
} else {
currentChar = newChar
segmentLen++
result += strings.ToLower(string(newChar))
}
isVowel, isConsonant := ppCharType(currentChar)
if isVowel {
vowelCount++
consoCount = 0
}
if isConsonant {
vowelCount = 0
if newSegment {
consoCount = ppMaxRepeatedConsonant
} else {
consoCount++
}
}
}
return result, entropy
}
func PronouncablePassword(len int) string {
v, _ := PronouncablePasswordExt(rand.Reader, len)
return v
}
func PronouncablePasswordSeeded(seed int64, len int) string {
v, _ := PronouncablePasswordExt(mathrand.New(mathrand.NewSource(seed)), len)
return v
}