main.go

package main

import (
	"bufio"
	"fmt"
	"math/rand"
	"os"
	"strings"
	"time"
)

func main() {
	//Initialize letters slice and map of letters
	letters := []string{"A", "B", "C", "D", "E",
		"F", "G", "H", "I", "J", "K", "L", "M",
		"N", "O", "P", "Q", "R", "S", "T",
		"U", "V", "W", "X", "Y", "Z"}
	letters_map := make(map[string]int)
	for i := 0; i < len(letters); i++ {
		letters_map[letters[i]] = i
	}

	//Create the vigenere square
	var square [26][26]string

	k := 0
	//loop through rows
	for i := 0; i < 26; i++ {
		//loop through columns
		for j := 0; j < 26; j++ {
			k = (i + j) % 26
			square[i][j] = letters[k]
		}
	}

	fmt.Println("Do you want to:")
	fmt.Println("1: Encrypt Message")
	fmt.Println("2: Decrypt Message")

	reader := bufio.NewReader(os.Stdin)
	char, _, err := reader.ReadRune()

	if err != nil {
		fmt.Println(err)
	}

	switch char {
	case '1':
		key := ""
		//initiate a new seed on runtime, and use it as seed for random generator
		source := rand.NewSource(time.Now().UnixNano())
		gen := rand.New(source)
		fmt.Println("Random Keys:")
		//print 4 random keys of length 8
		for i := 0; i < 4; i++ {
			key = "" //reset key
			for j := 0; j < 8; j++ {
				key += letters[gen.Intn(26)]
			}
			//Print out the key
			fmt.Printf("Key %v: %v\n", i, key)
		}

		fmt.Println("Please enter a key to use for encryption:")

		reader := bufio.NewReader(os.Stdin)
		raw_key, _ := reader.ReadString('\n')
		// print out confirmation
		fmt.Printf("You have entered key: %v", raw_key)

		fmt.Println("Please enter a plaintext message:")

		raw_plaintext, _ := reader.ReadString('\n')
		// print out confirmation
		fmt.Printf("You have entered text: %v", raw_plaintext)

		clean_key := strings.TrimSpace(strings.ToUpper(strings.Replace(raw_key, " ", "", -1)))
		clean_plaintext := strings.TrimSpace(strings.ToUpper(strings.Replace(raw_plaintext, " ", "", -1)))

		//if key is longer than plaintext, truncate
		if len(clean_key) > len(clean_plaintext) {
			clean_key = clean_key[:len(clean_plaintext)]
		}

		key_text := ""
		for len(key_text) < len(clean_plaintext) {
			key_text += clean_key
		}
		if len(key_text) > len(clean_plaintext) {
			key_text = key_text[:len(clean_plaintext)]
		}

		ciphertext := ""
		for i := 0; i < len(clean_plaintext); i++ {
			ciphertext += square[letters_map[string(key_text[i])]][letters_map[string(clean_plaintext[i])]]
		}
		fmt.Printf("Cleaned and formatted Key: %v\n", clean_key)
		fmt.Printf("Cleaned and formatted Plaintext: %v\n", clean_plaintext)
		fmt.Printf("Cleaned and formatted Keytext: %v\n", key_text)
		fmt.Printf("Cleaned and formatted Ciphertext: %v\n", ciphertext)
		break
	case '2':
		fmt.Println("Please enter a key to use for decryption:")

		reader := bufio.NewReader(os.Stdin)
		raw_key, _ := reader.ReadString('\n')
		// print out confirmation
		fmt.Printf("You have entered key: %v", raw_key)

		fmt.Println("Please enter a ciphertext message:")

		raw_ciphertext, _ := reader.ReadString('\n')
		// print out confirmation
		fmt.Printf("You have entered text: %v", raw_ciphertext)

		clean_key := strings.TrimSpace(strings.ToUpper(strings.Replace(raw_key, " ", "", -1)))
		clean_ciphertext := strings.TrimSpace(strings.ToUpper(strings.Replace(raw_ciphertext, " ", "", -1)))

		//if key is longer than ciphertext, truncate
		if len(clean_key) > len(clean_ciphertext) {
			clean_key = clean_key[:len(clean_ciphertext)]
		}

		key_text := ""
		for len(key_text) < len(clean_ciphertext) {
			key_text += clean_key
		}
		if len(key_text) > len(clean_ciphertext) {
			key_text = key_text[:len(clean_ciphertext)]
		}

		plaintext := ""
		for i := 0; i < len(clean_ciphertext); i++ {
			for j := 0; j < 26; j++ {
				if square[letters_map[string(key_text[i])]][j] == string(clean_ciphertext[i]) {
					plaintext += letters[j]
					break
				}
			}
		}
		fmt.Printf("Cleaned and formatted Key: %v\n", clean_key)
		fmt.Printf("Cleaned and formatted Ciphertext: %v\n", clean_ciphertext)
		fmt.Printf("Cleaned and formatted Keytext: %v\n", key_text)
		fmt.Printf("Cleaned and formatted Plaintext: %v\n", plaintext)
		break
	}
}