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Questions and Answers
Which type of attack involves observing the decrypted plaintext from chosen input ciphertext?
Which type of attack involves observing the decrypted plaintext from chosen input ciphertext?
What directly influences the security of a cipher in relation to key management?
What directly influences the security of a cipher in relation to key management?
Which attack technique exploits the relationship between differences in input and output of a cipher?
Which attack technique exploits the relationship between differences in input and output of a cipher?
What is the main principle behind birthday attacks in cryptography?
What is the main principle behind birthday attacks in cryptography?
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Which aspect is NOT a crucial part of effective key management in cryptographic systems?
Which aspect is NOT a crucial part of effective key management in cryptographic systems?
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What operation is used to combine the keystream with plaintext in stream ciphers?
What operation is used to combine the keystream with plaintext in stream ciphers?
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Which of the following best describes how block ciphers operate?
Which of the following best describes how block ciphers operate?
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Which encryption method uses the same key for both encryption and decryption?
Which encryption method uses the same key for both encryption and decryption?
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What type of cryptographic attack occurs when the attacker only has standard ciphertext?
What type of cryptographic attack occurs when the attacker only has standard ciphertext?
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Which of the following is a security property unique to the Cipher Block Chaining (CBC) mode of operation?
Which of the following is a security property unique to the Cipher Block Chaining (CBC) mode of operation?
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What is the main function of Message Authentication Codes (MACs)?
What is the main function of Message Authentication Codes (MACs)?
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Which asymmetric-key cryptography example is primarily used for secure key exchange?
Which asymmetric-key cryptography example is primarily used for secure key exchange?
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What distinguishes hash functions from traditional encryption methods?
What distinguishes hash functions from traditional encryption methods?
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The hash value in bits for MD5 is _____?
The hash value in bits for MD5 is _____?
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IPSec ______ mode involves encryption from gateway to gateway?
IPSec ______ mode involves encryption from gateway to gateway?
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Chaskey is a lightweight cryptography method used for _____?
Chaskey is a lightweight cryptography method used for _____?
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The minimum recommended key size to use with RC4 is _____ bits?
The minimum recommended key size to use with RC4 is _____ bits?
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What has a block size of 64 bits and key size of 56 bits?
What has a block size of 64 bits and key size of 56 bits?
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A(n) _____ is a collection of precomputed hash values of actual plaintext passwords?
A(n) _____ is a collection of precomputed hash values of actual plaintext passwords?
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Which encryption method allows for a variable key size up to a maximum of _____ bits?
Which encryption method allows for a variable key size up to a maximum of _____ bits?
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Key sizes used with the Advanced Encryption Standard (AES) include _____?
Key sizes used with the Advanced Encryption Standard (AES) include _____?
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What is a primary function of One Time Passwords (OTP)?
What is a primary function of One Time Passwords (OTP)?
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Which key method is used to establish a secure connection in SSL/TLS?
Which key method is used to establish a secure connection in SSL/TLS?
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Which protocol number is assigned for the encapsulating security protocol (ESP) in IPSec?
Which protocol number is assigned for the encapsulating security protocol (ESP) in IPSec?
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What do miners receive as a reward for their mining efforts in blockchain technology?
What do miners receive as a reward for their mining efforts in blockchain technology?
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Ethereum and Hyperledger are considered common options for implementing _____.
Ethereum and Hyperledger are considered common options for implementing _____.
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During which certificate management stage does validation occur?
During which certificate management stage does validation occur?
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The Bifid cipher makes use of a grid to map letters into numeric values. What type of cipher is it?
The Bifid cipher makes use of a grid to map letters into numeric values. What type of cipher is it?
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What is the main function of an Online Certificate Status Protocol (OCSP)?
What is the main function of an Online Certificate Status Protocol (OCSP)?
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What is a defining characteristic of a 'Cut-and-paste' attack?
What is a defining characteristic of a 'Cut-and-paste' attack?
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What is the block size for AES?
What is the block size for AES?
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Which method allows government agents to potentially decrypt secure communication without the knowledge of the data owners?
Which method allows government agents to potentially decrypt secure communication without the knowledge of the data owners?
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Which block cipher mode exposes AES to a copy-and-paste attack?
Which block cipher mode exposes AES to a copy-and-paste attack?
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What is the key size for 3DES?
What is the key size for 3DES?
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What key concept does the term 'gas' refer to in Ethereum applications?
What key concept does the term 'gas' refer to in Ethereum applications?
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During what stage of certificate management does certificate expiration occur?
During what stage of certificate management does certificate expiration occur?
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The Paillier cryptosystem supports _____ encryption.
The Paillier cryptosystem supports _____ encryption.
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What is the primary function of hash algorithms like SHA1 and MD5?
What is the primary function of hash algorithms like SHA1 and MD5?
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Which version of Elliptic Curve cryptography supports symmetric key exchange?
Which version of Elliptic Curve cryptography supports symmetric key exchange?
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With NTLM, each character in a password is converted into _____.
With NTLM, each character in a password is converted into _____.
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Which of the following best describes a 'Man-in-the-middle (MITM)' attack?
Which of the following best describes a 'Man-in-the-middle (MITM)' attack?
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What does the term 'exhaustive search' refer to in cryptography?
What does the term 'exhaustive search' refer to in cryptography?
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What does a digital certificate prove in HTTPS communications?
What does a digital certificate prove in HTTPS communications?
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Which block cipher mode enables parallel processing of data blocks?
Which block cipher mode enables parallel processing of data blocks?
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In symmetric cryptography, which aspect is better suited for real-time communications than asymmetric cryptography?
In symmetric cryptography, which aspect is better suited for real-time communications than asymmetric cryptography?
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PKCS #5 is a standard used for _____.
PKCS #5 is a standard used for _____.
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What initialization vector (IV) value does WPA-supported TKIP use?
What initialization vector (IV) value does WPA-supported TKIP use?
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El Gamal is used for _____.
El Gamal is used for _____.
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Which key should be shared or distributed to facilitate decryption in asymmetric cryptography?
Which key should be shared or distributed to facilitate decryption in asymmetric cryptography?
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What is the purpose of block cipher modes in symmetric encryption?
What is the purpose of block cipher modes in symmetric encryption?
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Which symmetric block cipher modes operate similarly to stream ciphers?
Which symmetric block cipher modes operate similarly to stream ciphers?
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What component do symmetric block ciphers use to perform substitution during encryption?
What component do symmetric block ciphers use to perform substitution during encryption?
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What is the block size of the PRESENT cipher?
What is the block size of the PRESENT cipher?
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What is the key size used with Skipjack, a symmetric block cipher?
What is the key size used with Skipjack, a symmetric block cipher?
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IDEA cipher has specific characteristics including a block size of 64 bits and a key size of 128 bits. Which of the following is true about it?
IDEA cipher has specific characteristics including a block size of 64 bits and a key size of 128 bits. Which of the following is true about it?
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What type of cryptography uses a key pair for encryption and decryption?
What type of cryptography uses a key pair for encryption and decryption?
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What is the block size used with RC5, a symmetric block cipher?
What is the block size used with RC5, a symmetric block cipher?
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When encrypting data with symmetric cryptography, which key is typically exchanged?
When encrypting data with symmetric cryptography, which key is typically exchanged?
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What is the minimum recommended key size when employing RC2?
What is the minimum recommended key size when employing RC2?
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What is the maximum key size for the RC5 cipher?
What is the maximum key size for the RC5 cipher?
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Which lightweight cryptography method is used for signing messages (MAC)?
Which lightweight cryptography method is used for signing messages (MAC)?
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What implementation is optimized for low-power operations in embedded systems?
What implementation is optimized for low-power operations in embedded systems?
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Which encoding scheme for x.509 certificates supports Base64 format?
Which encoding scheme for x.509 certificates supports Base64 format?
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What type of cipher is Blowfish categorized as?
What type of cipher is Blowfish categorized as?
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What is the block size used with XTEA?
What is the block size used with XTEA?
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What is the IV length used in the WEP encryption standard?
What is the IV length used in the WEP encryption standard?
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What cryptographic method involves creating a unique passcode based on a specific time period?
What cryptographic method involves creating a unique passcode based on a specific time period?
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What must an entity generate to obtain a digital certificate?
What must an entity generate to obtain a digital certificate?
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What defines a Mono-alphabetic substitution cipher?
What defines a Mono-alphabetic substitution cipher?
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Which light-weight cryptographic cipher is optimized for hardware implementations?
Which light-weight cryptographic cipher is optimized for hardware implementations?
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What unique capability does homomorphic encryption provide?
What unique capability does homomorphic encryption provide?
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What key size is typically associated with WEP?
What key size is typically associated with WEP?
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What type of encoding supports up to 65,536 characters?
What type of encoding supports up to 65,536 characters?
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What is the main feature of symmetric block ciphers?
What is the main feature of symmetric block ciphers?
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What is the primary risk associated with a collision in hashing?
What is the primary risk associated with a collision in hashing?
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Which cipher is known for being unbreakable since it uses its cipher code only once?
Which cipher is known for being unbreakable since it uses its cipher code only once?
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Study Notes
Introduction to Cryptography
- Cryptography secures communication and data by transforming it into an unreadable format.
- Key techniques encode and decode information to protect confidentiality, integrity, and authenticity.
- Fundamental components include encryption/decryption algorithms and key management for secure communication.
Keystream
- A keystream is a pseudo-random bit sequence generated by a PRNG.
- Combining keystream with plaintext (XOR) creates ciphertext.
- Decryption uses the same keystream (XOR).
Block Ciphers
- Block ciphers encrypt fixed-size plaintext blocks independently.
- Common modes: Electronic Codebook (ECB), Cipher Block Chaining (CBC), Output Feedback (OFB), and Counter (CTR). Each mode has security properties. ECB is vulnerable to copy-and-paste attacks.
- Feistel networks use substitution-permutation networks (SPN).
Encryption Methods
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Symmetric-key cryptography: Same key for encryption/decryption. Examples: AES, DES, Blowfish, Skipjack, IDEA, RC6, Camelia, 3DES.
- AES uses 128, 192, or 256 bit keys, operates in 128 bit blocks.
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Asymmetric-key cryptography: (Public-key cryptography) Different keys for encryption/decryption. Examples: RSA, ECC, Diffie-Hellman, Cramer-Shoup.
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Hash functions: Transform any-length input into a fixed-size hash. Crucial for message integrity. MD5 (128 bits), SHA-1 (160 bits), SHA-256 (256 bits are some examples), as well as non-cryptographic hashing solutions such as Bernstein, Buzhash, Cityhash, and Spookyhash. Quark produces 64 or 112 bit hash values. MD4 (128 bits).
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Stream ciphers: Encrypt bit-by-bit using a keystream. RC4 (40, 128 bits max key size, min 40 bits recommended), ChaCha, Trivium, Rabbit, Mickey v2, Grain are examples. AES 128, 192, or 256 bits. Considered less secure than AES for modern use cases.
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Message Authentication Codes (MACs): Generate unique codes for message integrity and authenticity. Chaskey (128-bit key), lightweight MAC.
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Key exchange: Diffie-Hellman, Elliptic Curve (Elli) are used for key exchange. Supports symmetric key establishment.
Cryptographic Attacks
- Ciphertext-only attacks: Only ciphertext.
- Known-plaintext attacks: Known plaintext-ciphertext pairs.
- Chosen-plaintext attacks: Choose plaintext, observe ciphertexts.
- Chosen-ciphertext attacks: Choose ciphertext, observe plaintexts.
- Brute-force attacks: Try all possible keys.
- Other attacks: Differential cryptanalysis, linear cryptanalysis, side-channel attacks, birthday attacks, rainbow tables (precomputed hashes of passwords).
Key Management
- Key management is critical.
- Processes for generation, distribution, storage, and key management.
- Secure key exchange protocols are employed for safe key establishment.
Security Considerations
- System security depends on strong algorithms, keys, and implementation.
- Security protocols require careful design and implementation to defend against attacks.
- Algorithm selection should match security needs.
Specific Cryptographic Algorithms
- Block Cipher Modes: CFB, OFB, CTR can make a block cipher function like a stream cipher.
- DES (Data Encryption Standard): Block size 64 bits, key size 56 bits, 16 rounds.
- 3DES (Triple DES): Block size 64 bits, key size 112 bits, 48 rounds.
- AES (Advanced Encryption Standard): 128 bit blocks, 128, 192, or 256 bit keys
- RC5: Block sizes 32, 64, or 128 bits; variable key size (up to 2048 bits).
- RC2: Block size 64 bits; variable key size up to 128 bits, minimum key size 40 bits recommended.
- Skipjack: 80 bit key, 64 bit block size
- IDEA: 64 bit block size, 128 bit key size, >17 rounds.
- PRESENT: 64 bit block size; 80 or 128 bit key size, 32 rounds.
- XTEA: 64-bit block size, 128-bit key size.
- CLEFIA: 128-bit blocks; 128, 192, or 256-bit keys.
- SIMON/SPECK: Lightweight block ciphers, optimized for hardware/software respectively.
- Rabbit: Symmetric stream cipher, 128-bit key size, 64-bit initialization vector (IV).
- Trivium: Symmetric stream cipher, 80-bit key size, 80-bit IV.
Special Algorithms
- Chaskey: Lightweight cryptography method for signing messages (MAC), ~3,333 gates at 1MHz clock rate, 128-bit key.
- HMAC: Message Authentication Code (MAC) that verifies message integrity and authenticity (Hashes message with secret key).
- IPSec transport/tunnel modes: Transport mode: end-to-end encryption; tunnel mode: encryption gateway-to-gateway.
- Hashing: Variable input length, fixed output length; uses salt to improve security against collisions (128, 160, 256 bits for e.g. MD5,SHA-1, SHA-256 respectively).
- One-Time Pad: Unbreakable, uses cipher code only once.
- Message Authentication Codes (MACs): Verify message integrity and authenticity, based on secret key and the message itself.
- Certificates (x.509): .cer, PEM, DER formats for certificates.
- Certificate Signing Request (CSR): Entity creates CSR to obtain a certificate. Authority signs with private key before issuing.
- Hash collisions: Two different inputs producing same hash.
- Initialization Vectors (IVs): Used in block cipher operations; commonly used in CFB, OFB, CTR modes.
- Homomorphic encryption: Perform mathematical operations on ciphered values.
- Key escrow: Keeps backup copies of cryptographic keys, raising privacy concerns, a backdoor condition.
- Public-key cryptography: uses a key pair for encryption and decryption; one is public, the other is private.
- Password cracking tools: Rainbow tables: collection of precomputed hashes of passwords for cracking.
- One-Time Passwords (OTPs): HOTP (hashed), TOTP (timed) methods for generating unique passcodes (used with 1-time passwords).
- WEP, WPA, WPA2: Different Wi-Fi encryption standards using varying key sizes and ciphers (RC4, AES). WEP:40 bit RC4 key, WPA: 128 bit RC4, WPA2: AES (128-bit block cipher) in their respective implementations.
Hardware Security Modules (HSMs) and Trusted Platform Modules (TPMs):
- HSMs manage cryptographic keys and provide cryptographic processing within a secure environment.
- TPMs are dedicated hardware processors handling hardware-level encryption for full disk encryption.
Data Encoding
- ASCII encoding: 8-bit values, 256 characters range.
- UTF-16 encoding: 16-bit values, 65,536 characters/range.
Standard Cipher Suites
- Various standards are available such as WEP, WPA, WPA2 with their associated symmetric algorithms, keys, and Initialization Vectors (IVs). These have been implemented for security in networking (using RC4 and AES ciphers).
Additional notes
- Conventional cryptography: used on servers, desktops & smartphones.
- Light-weight cryptography: used within embedded systems, RFID, sensor networks.
- Quantum computers: potential for breaking existing algorithms (especially RSA) due to fast multiplication circuits.
- IPSec Handshake: UDP port 500.
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Description
This quiz explores the foundational concepts of cryptography, including encryption, decryption, and keystreams. It delves into the mechanisms of block ciphers and the importance of securing communication. Test your understanding of how these techniques work to protect data.
