Taiga: Function privacy

[XuyangSong]

customer: @mariari performer: @XuyangSong deadline: null estimated: null started: null actual: null completed: null confirmed: null dependencies:

• [ ] Function privacy roadmap
• [ ] recursive zkp dependencies
• [ ] recursive zkp dependencies PRs
  • Poseidon sponge full duplex mode
  • Use Poseidon sponge in Halo2 transcript in prover and out-of-circuit verifier
• [ ] elaborate the function privacy in spec
• [ ] Integrate the function privacy to Taiga, a big refactor(ptx, tx, etc.) needs #149

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