Let EK: {0,1}128 → {0, 1}128 be an ideal block cipher with message space {0, 1}128, ciphertext space {0, 1}128, and key space {0, 1}128. Let x and y denote bitstrings of length 128. Is the following hash function H: {0, 17256 {0, 1}128 preimage resistant? → H(x, y) = Ey(y) Or

Let EK: {0,1}128 → {0, 1}128 be an ideal block cipher with message space {0, 1}128, ciphertext space {0, 1}128, and key space {0, 1}128. Let x and y denote bitstrings of length 128. Is the following hash function H: {0, 17256 {0, 1}128 preimage resistant? → H(x, y) = Ey(y) Or

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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Question

Let \( E_K : \{0,1\}^{128} \rightarrow \{0,1\}^{128} \) be an *ideal* block cipher with message space \(\{0,1\}^{128}\), ciphertext space \(\{0,1\}^{128}\), and key space \(\{0,1\}^{128}\). Let \( x \) and \( y \) denote bitstrings of length 128. Is the following hash function \( H : \{0,1\}^{256} \rightarrow \{0,1\}^{128} \) preimage resistant?

\[
H(x, y) = E_y(y) \oplus x
\]

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Hash function

The purpose of a hash function is to fit a set of inputs of any size into the a table or even other data structure with fixed-size elements.

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