RFC 4835 - Cryptographic Algorithm Implementation Requirements for Encapsulating Security Payload (ESP) and Authentic

ation Header (AH)

Speaker:ChungYi Wang

Advister:Quincy Wu

2007/4/23

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Outline

Motivation ESP & AH ESP & AH table Changes from RFC 2402 and RFC 2406 to

RFC 4305 Changes from RFC 4305 Reference

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Motivation

The IPsec series of protocols makes use of various cryptographic algorithms in order to provide security services.

To ensure interoperability between disparate implementations, it is necessary to specify a set of mandatory-to- implement algorithms to ensure that there is at least one algorithm that all implementations will have available.

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ESP & AH(1/3)

Encapsulating Security Payload (ESP)– 內容保密

Authentication Header (AH)– 身分認證，重送確認

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ESP & AH(2/3)

AH

http://en.wikipedia.org/wiki/IPsec#Encapsulated_Security_Payload_.28ESP.29

IP address, key …

Integrity Check Value

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ESP & AH(3/3)

ESP

http://en.wikipedia.org/wiki/IPsec#Encapsulated_Security_Payload_.28ESP.29

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ESP & AH table(1/7)

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ESP & AH table(2/7)

SHOULD+– 未來可能變成 MUST

SHOULD-– 未來可能變成 MAY

MUST-– 未來可能不再是 MUST

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ESP & AH table - DES(3/7)

DES (Data Encryption Standard)– small key size(56bits), publicly demonstrated,

open-design special-purpose cracking hardware

Questionable security for general use

TripleDES– Key size:168 bits– Rounds:48 DES-equivalent rounds

http://en.wikipedia.org/wiki/TripleDES

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ESP & AH table - AES(4/7)

AES (Advanced Encryption Standard)– NIST 宣佈，於 1998 第一次提出，也就是 Rijnda

el– Key Size:128bits, 192bits, 256bits– Block size:128bits

– 於軟體和硬體上的運算都很快 , 容易實作 , 並且不需要太多的記憶體操作。

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ESP & AH table - HMAC(5/7)

HMAC (keyed-hash message authentication code)– 利用雜湊函式進行 身分驗證，資料完整性的演算法。

MD5– Digest size:128bits– Rounds:4

SHA-1– Digest size:128bits– Rounds:80

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ESP & AH table - Collision(6/7)

H(x) = H(y)– X 不等於 y– 不同來源卻有相同的認證 hash

如果很不容易找到ㄧ對 x, y ，符合 H(x) = H(y) ，就是一個強壯的 (strong)雜湊函式演算法。

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ESP & AH table(7/7)

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Changes from RFC 2402 and RFC 2406 to RFC 4305

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Changes from RFC 4305

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Reference

RFC 4835– http://www.faqs.org/rfc/rfc4835.txt

IPsec (ESP & AH)– http://en.wikipedia.org/wiki/IPsec#Encapsulated_Security_Pa

yload_.28ESP.29

DES– http://en.wikipedia.org/wiki/Data_Encryption_Standard

AES– http://en.wikipedia.org/wiki/Advanced_Encryption_Standard– NIST:http://www.commerce.gov/opa/photo/NIST/events.html

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Reference

HMAC– http://en.wikipedia.org/wiki/HMAC– Hash collision : http://en.wikipedia.org/wiki/Hash_

collision

MD5– http://en.wikipedia.org/wiki/MD5

SHA1– http://en.wikipedia.org/wiki/SHA