Can I get Public Key from Private key with length 65 bits?

[Dimius555]

Can I get Public Key from Private key with length 65 bits?

[Dimius555]

Ok, sorry, I have just seen your new Readme and there I have found what I'm looking for! Thanks a lot!

[Dimius555]

As I read Public Key(65 bits) should be longer then private (32 bits)

[csjones]

Hey @Dimius555 👋

It seems you're looking for the .uncompressed public key format. Using the different format looks something like this:

secp256k1.Signing.PrivateKey(rawRepresentation: privateBytes, format: .uncompressed)

Here is a test I created with broader usage of the uncompressed public key format based on the data you provided.

let privateBytes = try! "703d3b63e84421e59f9359f8b27c25365df9d85b6b1566e3168412fa599c12f4".bytes
let privateKey = try! secp256k1.Signing.PrivateKey(rawRepresentation: privateBytes, format: .uncompressed)

XCTAssertEqual(privateKey.publicKey.format, .uncompressed)
XCTAssertEqual(privateKey.publicKey.rawRepresentation.count, secp256k1.Format.uncompressed.length)
        
let expectedPublicKeyString = """
 04c9c68596824505dd6cd1993a16452b4b1a13bacde56f80e9049fd03850cce137c1fa4acb7bef7edcc04f4fa29e071ea17e34fa07fa5d87b5ebf6340df6558498
"""

// Define the expected public key
let expectedPublicKey = try! expectedPublicKeyString.bytes

// Verify the generated public key matches the expected public key
XCTAssertEqual(expectedPublicKey, privateKey.publicKey.rawRepresentation.bytes)
XCTAssertEqual(expectedPublicKeyString, String(bytes: privateKey.publicKey.rawRepresentation.bytes))

[Dimius555]

Thank you @csjones!

But here is another issue, I see you are using secp256k1.Signing.PrivateKey, I'm trying to use secp256k1.KeyAgreement.PrivateKey and how can I create SharedSecret in this case?

[Dimius555]