Introduction Algebraic Structure Automated Tools Conclusion

Charles Bouillaguet

Description

Introduction Algebraic Structure Automated Tools Conclusion Automatic Search of Attacks on round-reduced AES and Applications Charles Bouillaguet Patrick Derbez Pierre-Alain Fouque ENS, CNRS, INRIA Cascade September 3, 2011

• block-cipher cryptanalysis


• block ciphers


• block cipher


• n? ??


• introduction algebraic


• widely-used block ciphers


• ciphertext pairs


• structure automated

Sujets

• Luis Ernesto Derbez Bautista
• Fouqué
• Block cipher

Informations

• Publié par: pefav
• Nombre de lectures: 10
• Langue: English

Extrait

nIrtoudtcoinlAegrbiactSurtcrueuAotametdoTlos AutomaticSearchofAttacks onround-reducedAESandApplications CharlesBouillaguetPatrickDerbezPierre-AlainFouque ENS,CNRS,INRIACascade September3,2011 oCcnulisno

nIrtoudtcoinlAegrbiactSurc Block-CipherCryptanalysis uter TheObject:aBlockCipher uAotametdoTlosoCn nnk E: | { 0 , {z 1 } } × | { 0 , {z 1 } } → | { 0 , {z 1 } } keyplaintextciphertext oftenk=n,butnotalways(e.g.AES-256:n=128andk=256) TheSubject:anAttacker I Objective:recoverthesecretkey (ormaybedistinguishfromrandom) I Resources: I Time:lessthan2 k encryptions I Data:lessthan2 n plaintext/ciphertextpairs TotalBreaksofwidely-usedblockciphersarerelativelyrare(in comparisonwithhashfunctions/streamciphers) lcsuoin

nIrtoudtcoinlAegrbiactSurtcrueuAotametdoTlos Whattodowhenblockciphersaretoostrongforus? K I Solution#1: I Firstweakenit I Thenbreakit KeySchedule k 0 k 1 k 2 k r Plaintext dnuoR Rdnuo dnuoR oRdnu Ciphertext oCcnulisno r(decueunbmrefoornusd)

nIrtoudtcoinlAegrbiactSurtcrueuAotametdoTlos Whattodowhenblockciphersaretoostrongforus? K I Solution#1: I Firstweakenit(reducenumberofrounds) I Thenbreakit KeySchedule k 0 k 1 k 2 k 3 Plaintext dnuoR nuoRd dnuoR dnuoR Ciphertext oCcnulisno