實現 zkSNARK 的 C++ 庫：libsnark

libsnark 是實現了 zkSNARK 模式的 C++ 庫。zkSNARK 是一個證明/驗證計算完整性的加密方法。

This library implements zkSNARK schemes, which are a cryptographic method for proving/verifying, in zero knowledge, the integrity of computations.

A computation can be expressed as an NP statement, in forms such as the following:

• "The C program foo, when executed, returns exit code 0 if given the input bar and some additional input qux."
• "The Boolean circuit foo is satisfiable by some input qux."
• "The arithmetic circuit foo accepts the partial assignment bar, when extended into some full assignment qux."
• "The set of constraints foo is satisfiable by the partial assignment bar, when extended into some full assignment qux."

A prover who knows the witness for the NP statement (i.e., a satisfying input/assignment) can produce a short proof attesting to the truth of the NP statement. This proof can be verified by anyone, and offers the following properties.

• Zero knowledge: the verifier learns nothing from the proof beside the truth of the statement (i.e., the value qux, in the above examples, remains secret).
• Succinctness: the proof is short and easy to verify.
• Non-interactivity: the proof is a string (i.e. it does not require back-and-forth interaction between the prover and the verifier).
• Soundness: the proof is computationally sound (i.e., it is infeasible to fake a proof of a false NP statement). Such a proof system is also called an argument.
• Proof of knowledge: the proof attests not just that the NP statement is true, but also that the prover knows why (e.g., knows a valid qux).

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