Exercise on key pairs for the Stark Curve

[tekkac]

Description

Show how to create stark_keys using a randomly generated private key.
Cairo has a python module for generating key pairs on the Stark curve.

Resource:

• https://github.com/starkware-libs/cairo-lang/blob/master/src/starkware/crypto/starkware/crypto/signature/signature.py
• https://perama-v.github.io/cairo/examples/verify_ecdsa/

Acceptance criteria

• The exercise show how to create stark keys
• The contract compiles and tests pass
• An exercise patch is generated