Go言語でRSAを実装してみる

package main

import (
    "fmt"
    "math/big"
)

type publicKey struct {
    E int
    N int
}

type privateKey struct {
    D int
    N int
}

func main() {
    publicKey, privateKey := generateKeys(101, 3259)
    plainText := "This is a secret"
    encryptedText := encrypt(plainText, publicKey)
    decryptedText := decrypt(encryptedText, privateKey)
    fmt.Println("Public Key:", publicKey.E, publicKey.N)
    fmt.Println("Private Key:", privateKey.D, privateKey.N)
    fmt.Println("Message:", plainText)
    fmt.Println("Encrypted Text:", encryptedText)
    fmt.Println("Decrypted Text:", decryptedText)
}

func generateKeys(p int, q int) (public publicKey, secret privateKey) {
    N := p * q
    L := lcm(p-1, q-1)
    var D, E int
    for i := 2; i < L; i++ {
        if gcd(i, L) == 1 {
            E = i
            break
        }
    }
    for i := 2; i < L; i++ {
        if (E*i)%L == 1 {
            D = i
            break
        }
    }
    return publicKey{E: E, N: N}, privateKey{D: D, N: N}
}

func lcm(p int, q int) int {
    return (p * q) / gcd(p, q)
}

func gcd(p int, q int) int {
    // https://play.golang.org/p/SmzvkDjYlb
    for q != 0 {
        t := q
        q = p % q
        p = t
    }
    return p
}

func encrypt(plainText string, publicKey publicKey) string {
    E, N := publicKey.E, publicKey.N
    resultString := ""
    for _, char := range plainText {
        bigChar := big.NewInt(int64(char))
        bigE := big.NewInt(int64(E))
        bigN := big.NewInt(int64(N))

        res := *bigChar.Exp(bigChar, bigE, bigN)
        resultString += string(rune(res.Int64()))
    }
    return resultString
}

func decrypt(encryptedText string, privateKey privateKey) string {
    D, N := privateKey.D, privateKey.N
    resultString := ""
    for _, char := range encryptedText {
        bigChar := big.NewInt(int64(char))
        bigD := big.NewInt(int64(D))
        bigN := big.NewInt(int64(N))

        res := *bigChar.Exp(bigChar, bigD, bigN)
        resultString += string(rune(res.Int64()))
    }
    return resultString
}

(master) ✗ go run main.go
Public Key: 7 329159
Private Key: 46543 329159
Message: This is a secret
Encrypted Text: 𕖜𪮖𸖗𳌒𣸲𸖗𳌒𣸲񍱄𣸲𳌒段𗁣񆏍段𫲮
Decrypted Text: This is a secret