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Getting started with the go language is simple: go implements the Caesar password
2022-07-04 13:49:00 【51CTO】
Use Caesar's password to move characters on text . call strings.Map Method .
1 Caesar code encryption
Caesar code （ English ：Caesar cipher）, Or Caesar encryption 、 Caesar transforms 、 Transform encryption , It's the simplest and most widely known encryption technology .
The Caesar code is a kind of Replace encryption technology , All the letters in the plaintext go backwards in the alphabet （ Or forward ） Offset by a fixed number and replaced with ciphertext . for example , When the offset is zero 3 When , All the letters A Will be replaced by D;B become E, And so on . This encryption method is named after Caesar in the Roman Republic , It is said that Caesar used this method to contact his generals .
Plaintext alphabet ：ABCDEFGHIJKLMNOPQRSTUVWXYZ Ciphertext alphabet ：DEFGHIJKLMNOPQRSTUVWXYZABC
design idea
- Set plaintext and move step size （ Secret text ）
- Convert clear text to lowercase , Prepare clear text byte slices and ciphertext slices
- Each plaintext character rotates according to the displacement step and is stored in the ciphertext
- Back to ciphertext
2 Go Realization
Caesar passwords are generally delivered in the form of passwords . Like this string of code “exxegoexsrgi” It's a password .
By moving the letters , We can encode messages . This prevents casual snooping . stay Go in , We can use strings.Map Method to achieve this .
2.1 Import package
2.2 To write caesar Method
Then let's write caesarEn() Caesar password encryption method . This will receive a string and return a modified string .
It moves characters , Then move the character to the valid range .
// Caesar code encryption
func
caesarEn(
strRaw
string,
step
byte)
string {
//1. Make text lowercase
str_raw :
=
strings.
ToLower(
strRaw)
//2. Define the step size
step_move :
=
step
//3. Convert a string to a plaintext character slice
str_slice_src :
= []
byte(
str_raw)
fmt.
Println(
"Clear text character slice:",
str_slice_src)
//4. Create a ciphertext character slice
str_slice_dst :
=
str_slice_src
//5. Loop through text slices
for
i :
=
0;
i
<
len(
str_slice_src);
i
++ {
//6. If the plaintext feature of the current period is within the displacement range , Please add a displacement step directly to save the ciphertext character slice
if
str_slice_src[
i]
<
123
-
step_move {
str_slice_dst[
i]
=
str_slice_src[
i]
+
step_move
}
else {
//7. If plaintext characters are out of range , Then add the step length after displacement and subtract 26
str_slice_dst[
i]
=
str_slice_src[
i]
+
step_move
-
26
}
}
//8. Output results
fmt.
Println(
"The encryption result is:",
step_move,
str_slice_dst,
string(
str_slice_dst))
return
string(
str_slice_dst)
}
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3 Caesar password decryption
thought ：
- Set ciphertext and displacement steps
- Prepare ciphertext character slice and plaintext character slice
- The characters of each ciphertext rotate according to the displacement step , And stored in the plaintext slice
- Return clear text
Go Caesar decrypts the code ：
//2. Caesar password decryption
func
caesarDe(
strCipher
string,
step
byte)
string {
//1. Make text lowercase
str_cipher :
=
strings.
ToLower(
strCipher)
//2. Alternate step size
step_move :
=
step
//3. Convert a string to a plaintext character slice
str_slice_src :
= []
byte(
str_cipher)
fmt.
Println(
"Ciphertext character slice:",
str_slice_src)
//4. Create a ciphertext character slice
str_slice_dst :
=
str_slice_src
//5. Loop through character text slices
for
i :
=
0;
i
<
len(
str_slice_src);
i
++ {
//6. If the plaintext feature of the current period is within the displacement range , Please add a displacement step directly to save the ciphertext character slice
if
str_slice_src[
i]
>=
97
+
step_move {
str_slice_dst[
i]
=
str_slice_src[
i]
-
step_move
}
else {
//7. If plaintext characters are out of range , Then add 26 Step length after subtracting displacement
str_slice_dst[
i]
=
str_slice_src[
i]
+
26
-
step_move
}
}
//8. Output results
fmt.
Println(
"The decryption result is:",
step_move,
str_slice_dst,
string(
str_slice_dst))
return
string(
str_slice_dst)
}
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4 Other implementations
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)
}
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5 test
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)
}
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Run the program ：
6 summary
This paper briefly introduces an interesting Caesar cipher in cryptography , The algorithm is an alternative encryption technology , And in Go The code implements the encryption and decryption process of the algorithm .
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