Flashcards
Crypto
Cards in this deck (30)
- 1Security GoalsAuthenticity
Integrity
Non-repudiation
Confidentiality - 2Security Goal vs. Crypto Techniques IntegrityHashing, Signatures
- 3Security Goal vs. Crypto Techniques Non-repudiationSignatures
- 4Security Goal vs. Crypto Techniques ConfidentialityEncryption
- 5Security Goal vs. Crypto Techniques Authenticity (Data)Keyed Hashing, Signature
- 6Security Goal vs. Crypto Techniques Authenticity (Entity)Special Protocols
- 73 Encryption SchemesSymmetric, Asymmetric. Hybrid
- 8Cryptosystems Facts(PCKED)
Plaintext units
Ciphertext units
Keys
Encryption Functions
Decryption Functions - 9Historical CiphersShift Cipher (Monoalphabetic)
Substitution Cipher (Monoalphabetic)
Vignere Cipher (Polyalphabetic)
Rotor Machines - 10Modern symmetric encryption SchemesBlock Chriffren
Stream Chiffren - 11Kerckhoffs PrincipleEverything is public concerning a crypto system
enables brute force attacks
Encryption Algorithm is safe altough the functions are publicly available - 12RSA vs AESKey is much larger than AES-Key
RSA is 180 times Slower than AES - 13RSA Problemcompute "m" for "m = c^d mod n"
mathematical: compute e-th root of mod n
In real life you couldnt factorize "m" in livetime, but if you could do this, RSA is broken - 14ConfusionRelationship between ciphertext and key
XOR with Key, S-Box
Nonlinear - 15DiffusionEvery ciphertext bit is attached on as many as possible plaintext bits
je mehr desto sicherer
Expansion, P-Box
Linear - 16Avalanche effectChanging one plaintext or key bit results in a new ciphertext
Is achieved by multiple rounds auf confusion and diffusion - 17Electronic Code Book (ECB) FactsBlock Cipher
DES/AES
Can be parallelized - 18Cipherblock Chaining (CBC) FactsUses XOR in Chains.
computes plaintext with IV in the first step, after that with the block before.
If one block broken, the following blocks are broken too. - 19Feistel NetworkIncludes DES as a round function (F)
Design Principles: Diffusion, confusion, avalanche in both directions - phases uses these principles - 20Data Encryption Standard (DES) factsBlock Lenght: 64 bit
Effective key: 56 bit - 21DES Round Key Generation16x 48-bit round keys
Permutated Choice 1 & 2
PC1: Input 64 bit
Output 56 bit
PC2: Input 56 bit repeated 16 times
output 48 bit keys - 22DES FunctionsExpansion, XOR with round key, Substitution, Permutation
- 23DES SecurityDES is weak because of the short key length
Brute Force is the best attack in practice - 24Triple-DES Securityencrypt a plaintext 3 times usign DES with different keys (Verschlüsseln, Entschlüsseln, Verschlüsseln)
provides security of a 112 bit key
Meet-in-the-middle attack is effective - it anihilates 56 bit - 25Advanced Encryption Standard (AES) FactsBlock length: 128 bit
Key length: 128,192,256 bit
based on Rijndael - 26AES FunctionsByte Substitution with S-Box, Shift Rows, Mix Columns. add round key
Decryption by conducting all steps in reverse order using inverse operations - 27RSA factsAsymmetric
Uses 4 Steps für Key Generation
RSA Problem
You could use RSA also for Signatures - 28RSA Key Generation1. Find Modulo n (n=p*q)
2. Find Public exponent e
3. Compute private exponent d (d=e^-1 mod ((p-1) * (q-1))
4. distribute public key - 29RSA SecurityBrute Force is effective
You could find p and q via factorisation
you could use extended euclidian algo to calculate d - 30Preimage ResistanceGiven a hash value H it is infeasible in practice to find an input wuth H=h(m)
Information
- Description
- Flashcards on Crypto, created by Tim Bender on 04/02/2020.
- Created by
- Tim Bender · Feb 2020
- Updated
- Feb 5, 2020
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