RFC 3602

RFC 3602
Title	RFC 3602
Type	Standards Track
Author	M. Schertler, S. Kent
Status	Historic
Year	2003

RFC 3602

RFC 3602 defines a specific method for the use of the Advanced Encryption Standard AES in Cipher Block Chaining CBC mode for securing Internet Protocol IP payloads. The document, authored by experts associated with the Internet Engineering Task Force and related to the Internet Protocol Security suite, specifies an encoding and padding approach intended to interoperate across implementations from vendors and organizations such as Cisco Systems, Juniper Networks, Microsoft Corporation, and IBM. It situates the AES-CBC construction within contemporary cryptographic practice alongside other algorithms developed by the National Institute of Standards and Technology, the Internet Architecture Board, and contributing researchers from academic institutions.

Introduction

This specification standardizes the use of the AES block cipher standardized by NIST in CBC mode for use with IPsec and related IETF protocols. The text clarifies parameters such as block size, initialization vector handling, and padding format to ensure consistent treatment by implementers at companies like Intel Corporation and Broadcom Corporation as well as by open-source projects associated with the Free Software Foundation and the Apache Software Foundation. It positions AES-CBC in relation to contemporaneous cipher modes evaluated by cryptographers from institutions including MIT, Stanford University, and University of California, Berkeley.

Background and Purpose

The background references the standardization path of AES after the competition run by NIST that selected the Rijndael algorithm. The document's purpose is to provide a concrete mode-of-operation pairing for AES within IPsec frameworks overseen by working groups in the IETF such as the IPsec Working Group and review processes involving reviewers from IANA and the Internet Society. It addresses compatibility concerns raised by vendors including Nortel Networks and standards bodies like the International Organization for Standardization and the Institute of Electrical and Electronics Engineers.

Algorithm Specification

The specification prescribes AES with a 128-bit block size operating in CBC mode with an explicit IV. It details the padding bytes appended to plaintext prior to encryption, aligning with practices used in implementations by OpenSSL Project and stacks deployed by Red Hat and Canonical Ltd.. The document enumerates key lengths of 128, 192, and 256 bits as defined in the AES standard promulgated by NIST and explains IV selection and transmission alongside Security Association parameters managed via protocols such as IKEv1 from the IETF and tools maintained by developers from Linux Foundation distributions. The algorithmic steps reference cryptanalytic evaluations contributed by researchers affiliated with RSA Laboratories, Bell Labs, and the Cryptography Research, Inc. community.

Security Considerations

The security section discusses the known limitations of CBC mode, such as IV reuse risks and padding oracle vulnerabilities identified in analyses by security researchers at University of California, Davis, Oxford University, and private firms including Mandiant and Kaspersky Lab. It recommends countermeasures like ensuring unique IVs per packet and prudent key management as practiced in deployments by Citrix Systems and cloud services run by Amazon Web Services and Google LLC. The document situates its guidance relative to alternative authenticated encryption mechanisms promoted by standards panels within IETF and research published in venues like the ACM and IEEE Transactions on Information Theory.

Interoperability and Implementation

Interoperability considerations cover message formats expected by implementations from networking equipment makers such as Huawei Technologies and Arista Networks and software stacks from projects like OpenBSD and FreeBSD. The specification aims to reduce ambiguity encountered in prior interoperability events involving vendors represented at Interop and tests run by independent laboratories accredited by ETSI. It includes recommendations for testing with suites derived from contributions by organizations including NIST and industry consortia like the Cloud Security Alliance.

Reception and Impact

Upon publication, the RFC influenced IPsec deployments across enterprises and service providers including AT&T, Verizon Communications, and major cloud platforms, and it informed product documentation from vendors like F5 Networks and Check Point Software Technologies. Over time, as the cryptographic community advanced authenticated encryption constructions championed by academics at École Polytechnique Fédérale de Lausanne and others, deployment guidance evolved to favor modes like Galois/Counter Mode promoted in later IETF work. The document remains a reference point for historical study of AES usage in IPsec stacks and for interoperability case studies conducted by standards organizations such as ITU and certification bodies like Common Criteria.

Category:Internet Standards