Generate Public key from Private Key using WebCrypto API

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I'm using Web Crypto API and am generating RSA Keypair using generateKey function. Because of some bugs in my code, I have deleted public key for some users. I'm wondering if there is any way to generate public key out of private key? I know that it's easily doable for ssh keys. Here is my sample code for generating RSA key pair:

const generateRSAKeys = (): Promise<CryptoKeyPair> => {
    return crypto.subtle.generateKey(
    {
        name: 'RSA-OAEP',
        modulusLength: 2048
        publicExponent: new Uint8Array([0x01, 0x00, 0x01]),
        hash: { name: 'SHA-512' },
    },
    true,
    ['encrypt', 'decrypt', 'wrapKey', 'unwrapKey'],
);
webcrypto-api encryption-asymmetric rsa encryption javascript
1 Answers

You can do it by exporting private key and importing exported data like public data

const keys = await crypto.subtle.generateKey(
  {
    name: 'RSA-OAEP',
    modulusLength: 2048,
    publicExponent: new Uint8Array([0x01, 0x00, 0x01]),
    hash: { name: 'SHA-512' },
  },
  true,
  ['encrypt', 'decrypt', 'wrapKey', 'unwrapKey'],
);

// export private key to JWK
const jwk = await crypto.subtle.exportKey("jwk", keys.privateKey);

// remove private data from JWK
delete jwk.d;
delete jwk.dp;
delete jwk.dq;
delete jwk.q;
delete jwk.qi;
jwk.key_ops = ["encrypt", "wrapKey"];

// import public key
const publicKey = await crypto.subtle.importKey("jwk", jwk, { name: "RSA-OAEP", 
hash: "SHA-512" }, true, ["encrypt", "wrapKey"]);

console.log(publicKey)

enter image description here

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