Node.js 利用 Web Crypto API 產生 RSA 公私鑰範例

index.js

const { subtle } = require("node:crypto").webcrypto;
const { writeFileSync } = require("node:fs");

subtle
    .generateKey(
        {
            name: "RSA-OAEP",
            modulusLength: 2048,
            publicExponent: new Uint8Array([1, 0, 1]),
            hash: "SHA-256"
        },
        true,
        ["encrypt", "decrypt"]
    )
    .then(async (key) => {
        console.log(key);
        writeFileSync("public.pem", await exportPublicKey(key.publicKey));
        writeFileSync("private.pem", await exportPrivateKey(key.privateKey));
    });

async function exportPrivateKey(key) {
    const exported = await subtle.exportKey("pkcs8", key);
    const exportedAsString = ab2str(exported);
    const exportedAsBase64 = btoa(exportedAsString);
    return `-----BEGIN PRIVATE KEY-----\n${exportedAsBase64}\n-----END PRIVATE KEY-----`;
}

async function exportPublicKey(key) {
    const exported = await subtle.exportKey("spki", key);
    const exportedAsString = ab2str(exported);
    const exportedAsBase64 = btoa(exportedAsString);
    return `-----BEGIN PUBLIC KEY-----\n${exportedAsBase64}\n-----END PUBLIC KEY-----`;
}

function ab2str(buf) {
    return String.fromCharCode.apply(null, new Uint8Array(buf));
}