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5 years ago

x - Faculty of Computer Science - Technische Universität Dresden

x - Faculty of Computer Science - Technische Universität Dresden

Security is asymmetric,

Security is asymmetric, too Digital signature system usually: unconditionally secure for recipient only cryptographically secure for signer new: signer is absolutely secure against breaking his signatures provable only cryptographically secure for recipient message domain signature domain x s s(x) � � proof of forgery � s‘(x) t true distribution of risks if signature is forged: 1. recipient 2. insurance or system operator 3. signer 254

x, s(x), “pass” or “fail” recipient plaintext with signature and test result plaintext with signature “accepted” or “forged” court Fail-stop signature system test verify t key for testing of signature, publicly known plaintext with signature x, s(x) plaintext with signature “accept” or proof of forgery key generation s sign generate proof of forgery 255 random number key for signing, kept secret plaintext x signer random number‘

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    Security in Computer Networks Multi

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    Areas of Teaching and Research •

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    5/48 Examples of changes w.r.t. ano

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    The massmedia „newspaper“ will

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    Multimedia Forensics

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    Multimedia Forensics

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    Areas of Teaching and Research •

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    15 General Aims of Education in IT-

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    General Aims of Education in IT-sec

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    General Aims of Education in IT-sec

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    …but no this way! First stupid an

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    Aims of Education: Offers by other

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    3 Cryptographic basics Table of Con

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    History of Communication Networks (

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    Important Terms computers interconn

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    threats: Threats and corresponding

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    confidentiality integrity availabil

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    commands universal universal Trojan

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    Which protection measures against w

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    money time Considered maximal stren

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    Strength of the attacker (model) At

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    Electromagentic radiation >dir AUTT

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    Why should I protect myself... ? ..

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    Previously on Security and Cryptogr

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    Multilateral security (2nd version)

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    Prevent the unintended Achieve the

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    Protection Goals: Definitions Confi

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    Correlations between protection goa

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    Physical security assumptions Each

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    Shell-shaped arrangement of the fiv

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    Golden rule Correspondence between

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    66 Lookahed: Why autentication: Adm

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    PIN protects access to chip New Ger

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    Identification of IT-systems by IT-

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    Password based authentication • S

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    One-way functions - cryptographic h

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    MD5 Hash in the Wild • United Sta

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    mission statement:= “USCYBERCOM p

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    Password based authentication • E

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    Remaining problems of password base

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    • main idea: Cryptanalytic Time -

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    • 2 nd example - breaking of PINs

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    Remaining problems of password base

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    Remaining problems of password base

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    Password based authentication • S

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    Password based authentication • S

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    Password based authentication • s

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    Password based authentication • s

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    Password based authentication • p

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    Password based authentication • (

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    • OTP Implementations - hash chai

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    Biometrics: Physiological / Behavio

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    • Enrolment phase: • Verificati

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    • Pros: Biometrics: Pros and Cons

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    • Pros: Biometrics: Pros and Cons

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    • Pros: Biometrics: Pros and Cons

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    ROC Curve and Security Problems of

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    Enhanced Security: Multi-biometric

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    Computer virus vs. transitive Troja

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    Further problems 1. Specify exactly

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    Aspects of distribution Distributed

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    Availability Infrastructure with th

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    more detailed notation Symmetric en

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    Key exchange using symmetric encryp

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    more detailed notation Domain of tr

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    more detailed notation Symmetric au

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    Key distribution using digital sign

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    Whom are keys assigned to? Comments

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    severity a) passive a1) ciphertext-

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    Basic facts about “cryptographica

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    Grundlagen - Sicherheit kryptograph

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    security information theoretic acti

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    Hybrid cryptosystems (2) Even more

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    Information-theoretically secure en

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    ciphertext S 00 01 10 11 equally di

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    154 Keys have to be very long for i

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    Definition for information-theoreti

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    Another definition for information-

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    Symmetric authentication systems (2

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    About cryptographically strong syst

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    clear: in NP � but difficulty can

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    Search of prime numbers (1) 1. Are

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    Z n : ring of residue classes mod n

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    Calculating with and without p,q (3

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    Compose ? Calculating with and with

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    Calculating with and without p,q (7

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    Calculating with and without p,q (9

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    Calculating with and without p,q (1

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    Calculating with and without p,q (1

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    Calculating with and without p,q (1

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    184 The s 2 -mod-n-Pseudo-random Bi

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    s 2 -mod-n-generator as symmetric e

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    s 2 -mod-n-generator as asymmetric

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    Security of the s 2 -mod-n-generato

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    Security of PBGs more precisely (1)

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    Security of PBGs more precisely (3)

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    constructive proof often Scheme of

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    Alg.2: has to demand uniformity Why

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    GMR - signature system (2) Construc

  • Page 199 and 200: To factor is difficult (1) Theorem:
  • Page 201 and 202: Solution of problem 1 (1) Tree of r
  • Page 203 and 204: Note In the proof you dispose the
  • Page 205 and 206: Key generation 1) Choose two prime
  • Page 207 and 208: Proof (2) Holds, of course, for m
  • Page 209 and 210: secret area plaintext x random numb
  • Page 211 and 212: secret area text with signature and
  • Page 213 and 214: ( x s ) Attack on digital signature
  • Page 215 and 216: Active Attack of Davida against RSA
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  • Page 219 and 220: Faster calculation of the secret op
  • Page 221 and 222: 64-bit block plaintext L 0 IP round
  • Page 223 and 224: L i-1 L i = R i-1 Decryption Why do
  • Page 225 and 226: Generation of a key for each of the
  • Page 227 and 228: L i-1 One round complement compleme
  • Page 229 and 230: Generalization of DES 1.) 56 � 16
  • Page 231 and 232: e.g. 64 bits with DES ECB Main prob
  • Page 233 and 234: Cipher Block Chaining (CBC) All lin
  • Page 235 and 236: � plaintext block n memory for ci
  • Page 237 and 238: Block length a Length of the output
  • Page 239 and 240: shift register 1 b CFB for authenti
  • Page 241 and 242: Plain Cipher Block Chaining (PCBC)
  • Page 243 and 244: Utilization of indeterministic bloc
  • Page 245 and 246: Diffie-Hellman key agreement (1) pr
  • Page 247 and 248: andom number 1 Domain of trust secr
  • Page 249: Find a generator in cyclic group Z
  • Page 253 and 254: Signature system for blindly provid
  • Page 255 and 256: Reconstruction of the secret: Thres
  • Page 257 and 258: adio television videophone phone in
  • Page 259 and 260: adio television videophone phone in
  • Page 261 and 262: Since about 1990 reality Video-8 ta
  • Page 263 and 264: Problems with exchanges Unsolved pr
  • Page 265 and 266: Questions: Attacker (-model) • Ho
  • Page 267: Questions: Attacker (-model) • Ho
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