AMCL JS ECDSA Key data structure and signing procedure

[CryptoMathician]

Hi,
in my example I want to create a key pair for ECDSA from a given byte seed and was searching for a data structure which holds the key pair and the keys in the library.
I am not sure, but it seems that it don't exist such a data structure right?
Should it not exist is it possible to add a data structure for it like for the RSA keys in rsa.js?
I was thinking about an object like KeyPair (Java) or something similar.

Thank you in advance!

Pascal

[CryptoMathician]

Or is it possible to store the generated key pair into the CryptoKeyPair object from the JS web crypto API [1]?
I am not sure, if that is possible.

Pascal

[1] https://developer.mozilla.org/en-US/docs/Web/API/CryptoKey

[mcarrickscott]

In general I like to keep public and secret keys separate from one another. The public key can always be generated from the secret key if needed.

[CryptoMathician]

Ok. Do you maybe know, if it is possible to import the created key from the library into the CryptoKeyPair/CryptoKey to use the standardized methods for signatures? Or is it possible to do the same behavior as in java (below) with this library?

Signature sig = Signature.getInstance("SHA256withECDSA");
		sig.initSign(privateKey);
		for(byte[] bytes : message) {
			sig.update(bytes);
		}
		return sig.sign();

The method sig.sign() gives me an byte array, but with the

ECDH.ECPSP_DSA(sha, rng ,privateKey,message,CS, DS);

I get the signature in form of CSand DS. Is it possible to create a signature as it is in java (above)?
The message is defined as follows:

List<byte[]> message

Thank you in advance!

EDIT:
In general I want to sign a nonce and a uid with the private key and want to get a byte array back.

[CryptoMathician]

Have I only to convert the CS (I think that is the r value) and DS (I thin it is the s value) [1] to a DER format like this example [2]

3045022065A67F8FF9CB5EA8BE899E94CB338FE09E2E596BC047D936FC2B96DC013B5DFC022100BE123D3F143AF91E4551AAFAE49C9187F64E323F5660D6C6198A9446C3F818A1

DER encoding:
30 - Sequence
45 - 45 hex bytes (69 decimal)
02 - Integer
20 - 20 hex bytes (32 decimal)
65A67F8FF9CB5EA8BE899E94CB338FE09E2E596BC047D936FC2B96DC013B5DFC - 32 bytes integer signature (r)
02 - Integer
21 - 21 hex (33 decimal) bytes
00BE123D3F143AF91E4551AAFAE49C9187F64E323F5660D6C6198A9446C3F818A1 - 33 bytes integer signature (s)

or is there something more to do? I am not sure, but it seems to me that the Java Signature object gives a byte array back, which are in DER format.

[1] https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm#Signature_generation_algorithm
[2] https://crypto.stackexchange.com/questions/78248/difference-between-der-encoded-signatures-in-javascript-java-and-c

[mcarrickscott]

I am sure it is possible, it seems just a case of transforming the signature from one format to another, but I'm afraid I don't have the time to look into it right now...

[CryptoMathician]

Ok, thank you anyway!