概要

任意のパスワードと暗号化したいテキストのみでPHPとJavaScriptで相互に暗号←→復号できる関数を示します。

PHP

encrypt.php

function encrypt(string $plaintext, string $passphrase) :string
    {
        $cipher = "aes-256-cbc";
        $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length($cipher));
        $key = hash('sha256', $passphrase, true);
        $encrypted = openssl_encrypt($plaintext, $cipher, $key, OPENSSL_RAW_DATA, $iv);
        $encrypted = base64_encode($iv . $encrypted);
        return $encrypted;
    }

decrypt.php

    function resvDecrypt(string $encryptedText, string $passphrase) :string
    {
        $cipher = "aes-256-cbc";
        $key = hash('sha256', $passphrase, true);
        $ivLength = openssl_cipher_iv_length($cipher);
        $data = base64_decode($encryptedText);
        $iv = substr($data, 0, $ivLength);
        $encrypted = substr($data, $ivLength);

        $decrypted = openssl_decrypt($encrypted, $cipher, $key, OPENSSL_RAW_DATA, $iv);
        return $decrypted;
    }

JavaScript

JavaScriptはcrypto-jsライブラリを使用します。

crypto-js

encrypt.js

import CryptoJS from 'crypto-js';

function encrypt(message, passphrase) {
    const key = CryptoJS.SHA256(passphrase);
    const iv = CryptoJS.lib.WordArray.random(16);
    const encrypted = CryptoJS.AES.encrypt(message, key, {
        iv,
        mode: CryptoJS.mode.CBC,
        padding: CryptoJS.pad.Pkcs7
    });
    const encryptedMessage = iv.concat(encrypted.ciphertext).toString(CryptoJS.enc.Base64);
    return encryptedMessage;
}

decrypt.js

import CryptoJS from 'crypto-js';

function decrypt(encryptedText, passphrase) {
    const encryptedBytes = CryptoJS.enc.Base64.parse(encryptedText);
    const iv = CryptoJS.lib.WordArray.create(encryptedBytes.words.slice(0, 4));
    const ciphertext = CryptoJS.lib.WordArray.create(encryptedBytes.words.slice(4));
    const key = CryptoJS.SHA256(passphrase);
    const decrypted = CryptoJS.AES.decrypt(
        { ciphertext },
        key,
        {
            iv,
            mode: CryptoJS.mode.CBC,
            padding: CryptoJS.pad.Pkcs7
        }
    );

    return decrypted.toString(CryptoJS.enc.Utf8);
}