4 其他实现
package main import ( "errors" "fmt" "reflect" "regexp" ) var TBL = []rune("abcdefghijklmnopqrstuvwxyz") var CLUES = []string{"this", "the", "that"} var ( ErrLength = errors.New("invalid length") ErrChar = errors.New("invalid char") ErrNoClue = errors.New("no clue word") ErrShift = errors.New("invalid shift value") ) func Encrypt(in string, sh int) (enc string, err error) { err = assert(in) if sh < 0 { err = ErrShift } if err != nil { return } enc = shift(in, sh) return } func Decrypt(in string) (dec string, sh int, err error) { err = assert(in) if err != nil { return } var hit bool = false subin := subStr(in) for i := 0; i < len(CLUES); i++ { subclue := subStr(CLUES[i]) for j := 0; j < len(subin)-len(subclue)+1; j++ { if reflect.DeepEqual(subin[j:j+1], subclue[0:len(subclue)-1]) { sh = subtract([]rune(in)[j], []rune(CLUES[i])[0]) hit = true break } } } if !hit { err = ErrNoClue return } dec = shift(in, -sh) return } func assert(in string) (err error) { if regexp.MustCompile(`[^a-z\. \r\n]`).MatchString(in) { err = ErrChar } else if len(in) > 80 { err = ErrLength } return } func shift(in string, sh int) (out string) { for _, v := range in { if v == '.' || v == ' ' || v == '\r' || v == '\n' { out += string(v) continue } i := indexOf(TBL, v) len := len(TBL) var ii int = (i + sh) % len if ii < 0 { ii += len } if ii > len { ii -= len } out += string(TBL[ii]) } return } func subtract(left rune, right rune) (out int) { l := indexOf(TBL, left) r := indexOf(TBL, right) out = l - r if out < 0 { out += len(TBL) } return } func subStr(in string) []int { subin := make([]int, 0, 79) for i := range in { if i > len(in)-2 { break } subin = append(subin, subtract([]rune(in)[i], []rune(in)[i+1])) } // return return subin } func indexOf(target []rune, searchChar rune) int { for i, v := range target { if v == searchChar { return i } } return -1 } func main() { in := "xlmw mw xli tmgxyvi xlex m xsso mr xli xvmt." fmt.Printf("in : '%s'\n", in) out, sh, err := Decrypt(in) fmt.Printf("out: '%s'\n", out) fmt.Printf("sh : %d\n", sh) fmt.Printf("err: %v\n", err) }
5 测试
package main import ( "fmt" "strings" ) func caesar(r rune, shift int) rune { // Shift character by specified number of places. // ... If beyond range, shift backward or forward. s := int(r) + shift if s > 'z' { return rune(s - 26) } else if s < 'a' { return rune(s + 26) } return rune(s) } func main() { value := "test" fmt.Println(value) // Test the caesar method in a func argument to strings.Map. value2 := strings.Map(func(r rune) rune { return caesar(r, 18) }, value) value3 := strings.Map(func(r rune) rune { return caesar(r, -18) }, value2) fmt.Println(value2, value3) value4 := strings.Map(func(r rune) rune { return caesar(r, 1) }, value) value5 := strings.Map(func(r rune) rune { return caesar(r, -1) }, value4) fmt.Println(value4, value5) value = "exxegoexsrgi" result := strings.Map(func(r rune) rune { return caesar(r, -4) }, value) fmt.Println(value, result) }
运行该程序:
test lwkl test uftu test exxegoexsrgi attackatonce
6 总结
本文简单介绍了一个有意思的密码学中的凯撒密码,该算法是一种替换加密技术,并在 Go 代码中实现了该算法的加密和解密过程。