Hash functions and signatures: Signature schemes are typically defined to work for a finite domain of possible message (the message spaces). Suppose you have a signature scheme S which is correct and secure (existentially unforgeable) for domain M={0,1}t, that is, S can be used to sign any t-bit
Hash functions and signatures: Signature schemes are typically defined to work for a finite domain of possible message (the message spaces). Suppose you have a signature scheme S which is correct and secure (existentially unforgeable) for domain M={0,1}t, that is, S can be used to sign any t-bit
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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Hash functions and signatures: Signature schemes are typically defined to work for a finite domain of possible message (the message spaces). Suppose you have a signature scheme S which is correct and secure (existentially unforgeable) for domain M={0,1}t, that is, S can be used to sign any t-bit message. Suppose you also have a hash function H which outputs t bits and is collision-resistant.
Consider a modified signature scheme S’ which can sign messages of unlimited length, where: S’.Sign(sk, m) = S.sign(sk, H(m))
Prove that this scheme is existentially unforgeable as long as S is existentially unforgeable and H is collision-resistant.
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