Cryptographic Client- Based Systems Flashcards
1
Q
Cryptography
A
- Study and practice of securing communications
- Encryption and hashing
- Provides confidentiality, integrity, peer authentication, and non repudiation
2
Q
Crytanalysis
A
- Study and practice of exploiting weaknesses in communications
- Provides confidentiality, integrity, peer authentication, and non repudiation
3
Q
Ciphers
A
- Algorithms used for encryption and decryption
- Outline the well - defined series of procedures that are followed
- Are many different types, from simple to complex
4
Q
Substitution Ciphers
A
- Replace one letter for another
- Substitutions can be based on a rotation scheme or other key
- ROT13 and Caesar cipher
5
Q
Poly-alphabetic Ciphers
A
- Replace letters using multiple substitution alphabets and character sets
6
Q
Transposition Ciphers
A
- Rearrange or per-mutate letters
- One example is Rail Fence Cipher
- Transposition is a common aspect of encryption algorithms with varying methods
7
Q
One Time PAD (OTP)
A
- One- Time random pre-shared key (PAD)
- Pure random keys are difficult to generate
- Often, PRNG key is added to plain text bits using modular addition
8
Q
Keys
A
- Ciphers, algorithms, and protocols are open source, so everyone knows
- Keys must be kept secret or cryptography fails
- Keys must be large to prevent a successful brute force attack
9
Q
Keys ( Continued)
A
- Manually generated
- Number generator
: Randon number generator (RNG)
: Pseudorandom number generator (PRNG) - Static keys
- Session keys
- Ephemeral keys
10
Q
Perfect forward Secrecy
A
- Compromises long-term keys (PMKs or CMKs), not any past session keys
- Protects past sessions against future compromises of secret keys or passwords
- A public- key crypto system has the optional property of forward secrecy when it generates one random secret key per session to complete a key agreement without using a deterministic algorithm
11
Q
Integrity and Cryptographic Hashing
A
- Maps data of any size to a fixed-length sting
: Also known as hash value, message digest, fingerprint, checksum - One-way mathematical function
: Produces a digest 128 to 512 bits in length
: No two message inputs should generate the same hash value (Collision)
12
Q
Hashing
A
- Authentication
- Data integrity
- Non repudiation
- Fingerprinting
- Password storage
: Password + Salt (or pepper) + hash function = hashed password
13
Q
Hashing Functions
A
- MD5 ( 128-bit digest produced)
- SHA-1 (160-bit digest produced)
- SHA- 2 and SHA-3
- RIPEMD (128-, 160-, 256-, 320-bit versions)
- Hashes are actually only half as strong as the key lengths due to the birthday paradox
14
Q
Symmetric Algorithms Explained
A
- Same secret key is used for encryption and decryption
- Secret key must be shared between sender and receiver securely
- Key is typically from 40 to 512 bits in length
15
Q
Symmetric Algorithms Methods
A
- DES
- 3DES
- RC4
- Blowfish / Twofish
- AES- 128, 192, and 256
