A hint for a prover which helps the prover to prove a statement. For example, if the statement is "pk1 && pk2",
and the prover knows only a secret for the public key pk1, the prover fails on proving without a hint. But if the
prover knows that pk2 is known to another party, the prover may prove the statement (with an empty proof for "pk2").
A hint for a prover which helps the prover to prove a statement. For example, if the statement is "pk1 && pk2", and the prover knows only a secret for the public key pk1, the prover fails on proving without a hint. But if the prover knows that pk2 is known to another party, the prover may prove the statement (with an empty proof for "pk2").