crypto

const hexToBytes = hex => new Uint8Array(hex.match(/.{1,2}/g).map(byte => parseInt(byte, 16)));
 
const deriveKey = async hexKey => {
    const rawKey = hexToBytes(hexKey);
    const baseKey = await crypto.subtle.importKey(
        "raw", rawKey, "HKDF", false, ["deriveKey"]
    );
    return crypto.subtle.deriveKey(
        {
            name: "HKDF",
            hash: "SHA-256",
            salt: new Uint8Array(16),
            info: new TextEncoder().encode("AES-GCM Key Derivation")
        },
        baseKey,
        { name: "AES-GCM", length: 256 },
        false,
        ["encrypt", "decrypt"]
    );
};
 
const encrypt = async (text, hexKey) => {
    const key = await deriveKey(hexKey);
    const iv = crypto.getRandomValues(new Uint8Array(12));
    const encoded = new TextEncoder().encode(text);
    
    const ciphertext = await crypto.subtle.encrypt(
        { name: "AES-GCM", iv: iv },
        key,
        encoded
    );
    
    const combined = new Uint8Array(iv.length + ciphertext.byteLength);
    combined.set(iv);
    combined.set(new Uint8Array(ciphertext), iv.length);
    return Array.from(combined).map(b => b.toString(16).padStart(2, '0')).join("");
};
 
const decrypt = async (hexCiphertext, hexKey) => {
    const key = await deriveKey(hexKey);
    const combined = hexToBytes(hexCiphertext);
    
    const iv = combined.slice(0, 12);
    const ciphertext = combined.slice(12);
    
    const decrypted = await crypto.subtle.decrypt(
        { name: "AES-GCM", iv: iv },
        key,
        ciphertext
    );
    
    return new TextDecoder().decode(decrypted);
};
 
(async (message) => {
    const myKey = window.app.appId;
    
    dv.paragraph(`元のメッセージ: ${message}`);
    
    const encryptedHex = await encrypt(message, myKey);
    dv.paragraph(`暗号化された16進数文字列: ${encryptedHex}`);
    
    const decryptedText = await decrypt(encryptedHex, myKey);
    dv.paragraph(`復号されたメッセージ ${decryptedText}`);
})("ここにテキスト");