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The RC5, RC5-CBC, RC5-CBC-Pad, and RC5-CTS Algorithms (RFC2040)

IP.com Disclosure Number: IPCOM000002595D
Original Publication Date: 1996-Oct-01
Included in the Prior Art Database: 2019-Feb-16
Document File: 29 page(s) / 34K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

R. Baldwin: AUTHOR [+1]

Related Documents

10.17487/RFC2040: DOI

Abstract

This document defines four ciphers with enough detail to ensure interoperability between different implementations. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 7% of the total text.

Network Working Group R. Baldwin Request for Comments: 2040 RSA Data Security, Inc. Category: Informational R. Rivest MIT Laboratory for Computer Science and RSA Data Security, Inc. October 1996

The RC5, RC5-CBC, RC5-CBC-Pad, and RC5-CTS Algorithms

Status of this Memo

This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

Acknowledgments

We would like to thank Steve Dusse, Victor Chang, Tim Mathews, Brett Howard, and Burt Kaliski for helpful suggestions.

Table of Contents

1. Executive Summary ....................... 1 2. Overview ................................ 2 3. Terminology and Notation ................ 3 4. Description of RC5 Keys ................. 4 5. Description of RC5 Key Expansion ........ 6 6. Description of RC5 Block Cipher ......... 10 7. Description of RC5-CBC and RC5-CBC-Pad .. 12 8. Description of RC5-CTS .................. 18 9. Test Program and Vectors ................ 19 10. Security Considerations ................. 26 11. ASN.1 Identifiers ....................... 28 References ........................................ 28 Authors’ Addresses ................................ 29

1. Executive Summary

This document defines four ciphers with enough detail to ensure interoperability between different implementations. The first cipher is the raw RC5 block cipher. The RC5 cipher takes a fixed size input block and produces a fixed sized output block using a transformation that depends on a key. The second cipher, RC5-CBC, is the Cipher Block Chaining (CBC) mode for RC5. It can process messages whose length is a multiple of the RC5 block size. The third cipher, RC5- CBC-Pad, handles plaintext of any length, though the ciphertext will be longer than the plaintext by at most the size of a single RC5

Baldwin & Rivest Informational [Page 1]

RFC 2040 RC5, RC5-CBC, RC5-CBC-Pad, and RC5-CTS October 1996

block. The RC5-CTS cipher is the Cipher Text Stealing mode of RC5, which handles plaintext of any length and the ciphertext length matches the plaintext length.

The RC5 cipher was invented by Professor Ronald L. Rivest of the Massachusetts Institute of Technology in 1994. It is a very fast and simple algorithm that is parameterized by the block size, the number of rounds, and key length. These parameters can be adjusted to meet different goals for security, performance, and exportability.

RSA Data Security Incorporated has filed a patent application on the RC5 cipher and for trademark protection for RC5, RC5-CBC, RC5-CBC- Pad, RC5-CTS and assorted variations.

2. Overview

This memo is a restatement of existing published material. The description of RC5 follows the notation and order of explanation found in the original RC5 paper by Professor Rivest [2]. The CBC mode appears in reference works such as the one by Bruce Schneier [6]. The CBC-Pad mode is the same as in the Public Key Cryptography Standard (PKCS) number five [5]. Sample C code [...

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