381 wire authentication

[NhoxxKienn]

Description

This PR serves to fix the #381 issue of Wire Authentication.

TLS Connection

Location: wire/net/simple

Issue: currently using TCP without TLS for communication.

Solution: Implement a simple mutual TLS Dialer and TLS Listener in the simple package, the default net wire for go-perun.

Bonus: A simple connection test has also been set up with self-signed Certificates in dialer_internal_test.go

Wire identity authentication

Location: wire/address.go, wire/account.go, and wire/net/exchange_addr.go, wire.proto

Issue: While each message currently contains a sender and recipient wire address in its Envelope, those are not yet authenticated; there is no signature in the wire.proto. This means anyone can send a message coming from SENDER, without needing the private key, thus allowing to spoof any wire identity.

Solution: Add Signing and Verifying for Account and Address. Like Wallet, the Account is expected to hold the private key, and the Address serves as the Public Key. Wire Authentication can be achieved by including a signature signed by the account in the AuthResponseMsg. Recipient can check the validity of this signature using the Sender Address (Public Key) to decrypt the signature.

Wire Authentication Implementation

Location: backend/sim/wire and wire/net/simple

Description: A simple implementation for the integration of key-pair to be used for wire authentication has been implemented in the testing and default wire.

For backend/sim/wire: This simple signing and verification of signature, independent from the given message.

For wire/net/simple: RSA-2048 Random-generated Key-Pair for (Account, Address), Signing of a given message by hashing and encrypting. Signature length: 256 Bits.

An address exchange test has also been added to the package to test the authentication function.

Visualization

[DragonDev1906]

I don't fully get why we need a separate field for the signature size, which is already in the byte slice and is encoded in protobuf. We can do it that way, I just don't see why we need/want an extra field.