Javascript window.crypto.subtle library returns an uncaught error when trying to decrypt ciphertext using imported key

Question

I am writing a script to decode a cipher text using a private key. The original text is Hello World . I used this website to generate the public private key pair, as well as testing the encryption: https://www.devglan.com/online-tools/rsa-encryption-decryption I chose the cipher type as RSA.

However, when I implemented this algorithm in JS, although I can import the private key, I always get an uncaught error as I try to decode the cipher text using the private key (ie window.crypto.subtle.decrypt()).

However, if I create the cipher text using the imported public key, I can decrypt it successfully. I suspect something is not right with how I converted string to uint8 array but I couldn't figure it out.

Using external JS library is not an option due to requirements. So as using public API endpoint for encryption/decryption. The script is going to be ran in a service worker.

Here is the code snippet

async function run(){

    const publicKey = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEApTsMkYN8ehigb/rHQSRm45kf6yPzxuMvihf6sx02+Kt7qCKCzfxETHG/bmczvK+j3GqBjgkYXSQ9pNtaXF5s5Bz9rk/4v/5GwYwk9WzH9GBc4XvLObQ84AQakG5UmnY5F6SWefgyWsPBkAIsaVUuTgV0iG8g6ubPXeOnINoRy5TxChTaKa1gyl0cqNG9QpKIfDfn7E7247Mb8+Yq1fjLTwnIYilhTuOOH3iVCGpaMDE9JcVIh6UojBFBRlcZcThJr1Ul3q9wLvmPhzTJ+AY5XMdqVULJNtnAi0SyfHkC82zf+WfW3s50B5RN3JfvR5qmO05wFTZn9aLOEflvTR3KcwIDAQAB"
    const privateKey = "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"
    const ciphertext = "CaLtZdaxgk55DMlExKyJvNa1S2CvN7yfb0txNViQvB9hX9YjhfmIyV/HAbAsdmM82Y27sQmF5VTe5XpFyt0fwxNVGarXGosbbtY3BEWk1fT15dWeVtgJ5Dmxf1cZ2fVVGNK9dtRcXpEdo0IUZqRi21u9ZC/wSEdbSHvHKx0UVO7Bq866LFv2E2F8/SNHCO6tCxPPPvI0RWSKDtA/Rj3lHkkMyUhcvjNhZbvr4jk40QlHhYfqh/hgCnNGVjDx1osTNe/OoRntFVILTPhlPSTTHKtw/UVIwulN4e8QApooDJGJYpK2daYh6BTN+XldWGcDEXP+YElKbF6mvEm5SRo+WQ=="

    const publicKeyCrypto = await importPublicKey(publicKey);
    const privateKeyCrypto = await importPrivateKey(privateKey);

    const dec = new TextDecoder()
    let cipherTextArr = fromBase64(ciphertext);
  

    decrypted = await window.crypto.subtle.decrypt(
      { 
        name: "RSA-OAEP"
      },
      privateKeyCrypto,
      cipherTextArr
    );
    console.log(dec.decode(decrypted))
}



const fromBase64 = base64String => Uint8Array.from(atob(base64String), c => c.charCodeAt(0));

async function importPrivateKey(key){
    return window.crypto.subtle.importKey(
        "pkcs8",
        fromBase64(key),
        {
          name: "RSA-OAEP",
          hash: "SHA-256",
        },
        true,
        ["decrypt"]
    );
}

async function importPublicKey(key){
  return window.crypto.subtle.importKey(
    "spki",
    fromBase64(key),
    {
      name: "RSA-OAEP",
      hash: "SHA-256"
    },
    true,
    ["encrypt"]
  );
}

Here is the error. The script is ran when I pressed the press me button. ( https://i.stack.imgur.com/KlRVq.png )

Appreciate any help from the community!

Answer 1

@Topaco Thank you very much for pointing that out. You are correct that I was using the wrong padding, After switching the Cipher Type to ESA/ECB/OAEPWithSHA-1AndMGF1Padding and changing the hash to 'SHA-1'. The problem is resolved.

async function importPrivateKey(key){
return window.crypto.subtle.importKey(
    "pkcs8",
    fromBase64(key),
    {
      name: "RSA-OAEP",
      hash: "SHA-1",
    },
    true,
    ["decrypt"]
    );
}