AES_GCM crypto

AES_GCM.js

const base64Key = 'your key base64 encode';
let secretKey;

function getKeyArray(key) {
    const bkey = atob(key);
    const keyArray = [];
    for (let i = 0; i < bkey.length; i += 1) {
        keyArray.push(bkey.charCodeAt(i));
    }
    return keyArray;
}

/*
    Import an AES secret key from an ArrayBuffer containing the raw bytes.
    Takes an ArrayBuffer string containing the bytes, and returns a Promise
    that will resolve to a CryptoKey representing the secret key.
*/
function importSecretKey() {
    const rawKey = new Uint8Array(getKeyArray(base64Key));
    return window.crypto.subtle.importKey(
        "raw",
        rawKey,
        "AES-GCM",
        true,
        ["encrypt", "decrypt"],
    );
}

async function encrypt(text) {
    if (!secretKey) {
        secretKey = await importSecretKey();
    }
    const iv = window.crypto.getRandomValues(new Uint8Array(12));
    const algorithm = {
        name: 'AES-GCM',
        iv: iv,
    };
    const enc = new TextEncoder();
    const ciphertext = await window.crypto.subtle.encrypt(algorithm, secretKey, enc.encode(text));
    const ciphertextUint8Array = new Uint8Array(ciphertext);
    const resultUint8Array = new Uint8Array(iv.byteLength + ciphertextUint8Array.byteLength);
    resultUint8Array.set(iv);
    resultUint8Array.set(ciphertextUint8Array, iv.byteLength);

    return btoa(String.fromCharCode.apply(null, resultUint8Array));
}

async function decrypt(encryptedText) {
    if (!secretKey) {
        secretKey = await importSecretKey();
    }
    const btext = new Uint8Array(getKeyArray(encryptedText));
    const iv = btext.slice(0, 12);
    const ciphertext = btext.slice(12, btext.length);

    const algorithm = {
        name: 'AES-GCM',
        iv: iv,
    };
    const result = await window.crypto.subtle.decrypt(
        algorithm,
        secretKey,
        ciphertext,
    );
    const dec = new TextDecoder();
    return dec.decode(result);
}

if (typeof window !== 'undefined') {

    encrypt('123').then(result => {
        console.log('encrypted', result);
        decrypt(result).then(decryptedText => {
            console.log('decrypted', decryptedText);
        })
    });

}