A verification context. Stores information involving the commitment values of inputs and outputs and it is used to verify the binding_sig. A context should created with init, passed to check_spend for all inputs and check_output for all outputs, passed to final_check and finally freed with free. *

Checks the zero-knowledge proof for spending money, the spend_sig, and stores info in the context. String is the anti-replay. *

Checks the zero-knowledge proof for creating money and stores information in the context *

Utilise the context to check the balance. String is the anti-replay string. *