Patent ID: 8245038

Claim:
A method for redacting content from a document and allowing a recipient to challenge the appropriateness of the redaction, the method comprising: redacting a string M i from a text location i in the document; producing a string R i from string M i by applying a trapdoor one-way function in the reverse direction, ƒ K −1 , based on a secret key K, wherein the input to the trapdoor one-way function in the reverse direction is at least based on M i ; producing a commitment C i =C(M i , R i ) for string M i using string R i as randomness; communicating the commitment C i to the recipient; receiving a challenge to the redacted string M i from the recipient, wherein the challenge indicates a topic string T; producing, by a computing device, a string R T from the topic string T by applying the trapdoor one-way function in the reverse direction, ƒ K −1 , based on the secret key K, wherein the input to the trapdoor one-way function in the reverse direction is at least based on T; and communicating string R T to the recipient, thereby allowing the recipient to determine whether the commitment C i corresponds to topic string T.