Method obfuscateSegment

backend/crypt/cipher.go:315–400

Simple obfuscation routines

(plaintext string)

// Simple obfuscation routines
func (c *Cipher) obfuscateSegment(plaintext string) string {
	if plaintext == "" {
		return ""
	}

	// If the string isn't valid UTF8 then don't rotate; just
	// prepend a !.
	if !utf8.ValidString(plaintext) {
		return "!." + plaintext
	}

	// Calculate a simple rotation based on the filename and
	// the nameKey
	var dir int
	for _, runeValue := range plaintext {
		dir += int(runeValue)
	}
	dir %= 256

	// We'll use this number to store in the result filename...
	var result bytes.Buffer
	_, _ = result.WriteString(strconv.Itoa(dir) + ".")

	// but we'll augment it with the nameKey for real calculation
	for i := range len(c.nameKey) {
		dir += int(c.nameKey[i])
	}

	// Now for each character, depending on the range it is in
	// we will actually rotate a different amount
	for _, runeValue := range plaintext {
		switch {
		case runeValue == obfuscQuoteRune:
			// Quote the Quote character
			_, _ = result.WriteRune(obfuscQuoteRune)
			_, _ = result.WriteRune(obfuscQuoteRune)

		case runeValue >= '0' && runeValue <= '9':
			// Number
			thisdir := (dir % 9) + 1
			newRune := '0' + (int(runeValue)-'0'+thisdir)%10
			_, _ = result.WriteRune(rune(newRune))

		case (runeValue >= 'A' && runeValue <= 'Z') ||
			(runeValue >= 'a' && runeValue <= 'z'):
			// ASCII letter.  Try to avoid trivial A->a mappings
			thisdir := dir%25 + 1
			// Calculate the offset of this character in A-Za-z
			pos := int(runeValue - 'A')
			if pos >= 26 {
				pos -= 6 // It's lower case
			}
			// Rotate the character to the new location
			pos = (pos + thisdir) % 52
			if pos >= 26 {
				pos += 6 // and handle lower case offset again
			}
			_, _ = result.WriteRune(rune('A' + pos))