数字签名与消息认证

座 3. Part Three Digital Signature and
Certification
Authority
4. Part Four Legal Responsibility
5. Part Six Supplementary Articles
Digital Signature Law is an
the validity of his signature
Requirements
信 息 安
• The signature depends on the signer and the document to be signed.
• Easy to compute: it is easy for a signer to sign a document
Infrastructure of E-COM
信
息
安
全
Supply Chain
讲 Online Payment
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Trading Platform
Credit System
Information Exchange Platform
Digital Signature Law is Infrastructure
信
息
二、基本签名算法
安
全
讲
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Fundamental schemes
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息 安
– Signature schemes based on errorcorrecting codes
全 讲
– Signature schemes based on two hard problems
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– Signature schemes based on elliptic curves
安 全
• Security requirements
讲
– Unforgeability: one cannot create a
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signature that is claimed to be another’s
– Undeniability: the signer cannot later deny
讲
• Forgery tye
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Leabharlann Baidu
– Existential forgery
– Selective forgery
The Model of Digital Signature
信 息 安 Signer’s 全 secret key 讲 座
Message
Sign Function
Verification Function
Signer’s public key
Signature Message
Message
Check Message=?Message
Digital signature: usage
信 • Off-line: Signing a document for emulating
息
the hand-written signature
What security service can digital
signature provide?
信
息
安
• Data Integrity
全
• Authentication
讲
• Non-forgeability
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• Non-repudiation
签名的一个重要应用 第三方信任的模型
信
息
证书认证中心(CA)
全
• Universal verifiability: every one can verify
讲
validity of a signature (with respect to the
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signer and the document)
• Easy to store: the signature should be short
讨论议题 ——数字签名
信
➢数字签名的概念
息
安 全
➢基本签名算法
讲
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➢特殊签名算法
➢研究动向
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一、数字签名的概念
安
全
讲
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Digital signature
信 • Goal: Use the digital technique to
息 emulate the “hand-written signature”
China Digital Signature Law have become effective
信
息
April 1 2005 China Digital Signature Law has become effective
安
全 1. Part One Overview
讲 2. Part Two Electronic Data
安
全
讲
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Fig. 信任的层次结构
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公正的被信任者
息
安
经认定可以
全
被信任的中
讲
间角色
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A
B
用户群
结论
信
网络空间的信任建立问题是信息安全讨
息
论的核心问题，网络空间的信任建立
安
方法很大程度上借鉴了传统生活中建
全 讲 座
立信任的方法。正如手写签名在传统 生活中的重要作用一样，数字签名是 网络空间中建立信任的一块基石。
安 • On-line: identity authentication (+session key
全
distribution)
讲
challenge c
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Alice
r=Sig(KRBob, c)
Bob
If Ver(KUBob, r, c)=true then accept that “Bob is talking to me”
Algorithm foundation
信
Two Famous Digital Signature Schemes
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1. RSA Digital signature scheme (based on the
安
factorization problem)
全
2. ElGamal digital signature and Meta-ElGamal
讲
signature schemes (based on the discrete logarithm)
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Some popular algorithms
enough
Attacks on digital signature
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• Attack type
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– Key-only attack (ciphertext-only)
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– Known-message attack (known-plaintext)
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– Chosen-message attack (chosen-plaintext)