End2End encryption IOException: algid parse error, not a sequence

I’m generating the Public and Private key by using the Native Browser crypto API as below:

export const generateKeyPair = async (): Promise<CryptoKeyPair> => {
    return await window.crypto.subtle.generateKey(
        {
            name: "ECDH",
            namedCurve: "P-384",
        },
        true,
        ["deriveKey", "deriveBits"],
    );
};

Then I’ll export the publicKey by using the exportKey function under the window.crypto.subtle as below:

const keyPair: CryptoKeyPair = yield generateKeyPair();
const publicKeyArrayBuffer: ArrayBuffer = yield window.crypto.subtle.exportKey("raw", keyPair.publicKey);
const publicKeyAsBase64 = arrayBufferToBase64(publicKeyArrayBuffer);

If you have any suggestions, please let me know and help me to fix this issue.

Answer

Both codes use different curves, the Java code secp256r1 (aka P-256), the JavaScript code P-384. To make both codes compatible, the JavaScript code must apply the same curve as the Java code, i.e. P-256 (s. also here).

The Java code exports a public EC key in X.509/SPKI format, which is Base64 encoded. The JavaScript code exports the public key in uncompressed format 0x04|<x>|<y>. The export in X.509/SPKI format is possible with spki as 1st parameter, s. here and here.