Questions and Answers
Cryptography is the practice and study of techniques for secure communication in the presence of third-party ______
adversaries
______-key cryptography uses the same secret key for both encryption and decryption
Symmetric
AES is an example of a ______ cipher
block
Hash functions are a type of one-way ______, cannot be decrypted
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Digital signatures use ______ cryptography to authenticate and ensure integrity of messages
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______ is ensuring data is not tampered with or altered
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A ______-plaintext attack is accessing both the encrypted and decrypted data
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HTTPS is an example of a secure online ______ that uses cryptography
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What is the main goal of cryptography?
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Describe the difference between symmetric-key and asymmetric-key cryptography.
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What is a block cipher and how does it operate?
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What are digital signatures used for in cryptography?
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Explain what a brute force attack entails in cryptographic terms.
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What is meant by the term 'ciphertext'?
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Define what a hash function does in the context of cryptography.
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What is a man-in-the-middle attack?
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Study Notes
What is Cryptography?
- The practice and study of techniques for secure communication in the presence of third-party adversaries
- encrypting plaintext (readable data) into ciphertext (unreadable data) to protect it from unauthorized access
Types of Cryptography
-
Symmetric-key cryptography: uses the same secret key for both encryption and decryption
- Examples: AES (Advanced Encryption Standard), DES (Data Encryption Standard)
-
Asymmetric-key cryptography: uses a pair of keys: a public key for encryption and a private key for decryption
- Examples: RSA (Rivest-Shamir-Adleman), elliptic curve cryptography
Cryptographic Algorithms
-
Block ciphers: encrypt data in fixed-length blocks
- Examples: AES, DES
-
Stream ciphers: encrypt data one bit or byte at a time
- Examples: RC4, FISH
-
Hash functions: one-way encryption, cannot be decrypted
- Examples: SHA-256, MD5
-
Digital signatures: use asymmetric cryptography to authenticate and ensure integrity of messages
- Examples: RSA, ECDSA (Elliptic Curve Digital Signature Algorithm)
Cryptographic Techniques
- Confidentiality: protecting data from unauthorized access
- Authentication: verifying the identity of the sender or recipient
- Integrity: ensuring data is not tampered with or altered
- Non-repudiation: ensuring a sender cannot deny sending a message
Cryptographic Attacks
- Ciphertext-only attack: accessing only the encrypted data
- Known-plaintext attack: accessing both the encrypted and decrypted data
- Chosen-plaintext attack: choosing the data to be encrypted
- Side-channel attack: attacking the implementation or environment of the cryptosystem rather than the algorithm itself
Cryptography Applications
- Secure online transactions (e.g., HTTPS)
- Secure communication protocols (e.g., SSL/TLS, IPsec)
- Digital currencies (e.g., Bitcoin)
- Secure email (e.g., PGP, S/MIME)
- Digital rights management (DRM)
What is Cryptography?
- Cryptography is the practice and study of techniques for secure communication in the presence of third-party adversaries.
- It involves encrypting plaintext (readable data) into ciphertext (unreadable data) to protect it from unauthorized access.
Types of Cryptography
Symmetric-key Cryptography
- Uses the same secret key for both encryption and decryption.
- Examples include AES (Advanced Encryption Standard) and DES (Data Encryption Standard).
Asymmetric-key Cryptography
- Uses a pair of keys: a public key for encryption and a private key for decryption.
- Examples include RSA (Rivest-Shamir-Adleman) and elliptic curve cryptography.
Cryptographic Algorithms
Block Ciphers
- Encrypt data in fixed-length blocks.
- Examples include AES and DES.
Stream Ciphers
- Encrypt data one bit or byte at a time.
- Examples include RC4 and FISH.
Hash Functions
- One-way encryption, cannot be decrypted.
- Examples include SHA-256 and MD5.
Digital Signatures
- Use asymmetric cryptography to authenticate and ensure integrity of messages.
- Examples include RSA and ECDSA (Elliptic Curve Digital Signature Algorithm).
Cryptographic Techniques
Confidentiality
- Protecting data from unauthorized access.
Authentication
- Verifying the identity of the sender or recipient.
Integrity
- Ensuring data is not tampered with or altered.
Non-repudiation
- Ensuring a sender cannot deny sending a message.
Cryptographic Attacks
Ciphertext-only Attack
- Accessing only the encrypted data.
Known-plaintext Attack
- Accessing both the encrypted and decrypted data.
Chosen-plaintext Attack
- Choosing the data to be encrypted.
Side-channel Attack
- Attacking the implementation or environment of the cryptosystem rather than the algorithm itself.
Cryptography Applications
- Secure online transactions (e.g., HTTPS).
- Secure communication protocols (e.g., SSL/TLS, IPsec).
- Digital currencies (e.g., Bitcoin).
- Secure email (e.g., PGP, S/MIME).
- Digital rights management (DRM).
Definition and Purpose
- Secure communication technique to protect against third-party adversaries
- Goals: confidentiality, integrity, and authenticity of messages
Basic Concepts
- Plaintext: original message or data to be protected
- Ciphertext: encrypted message or data, unreadable without decryption key
- Encryption: converting plaintext to ciphertext
- Decryption: converting ciphertext back to plaintext
- Key: piece of information for encryption and decryption
Types of Cryptography
-
Symmetric-key cryptography: same key for encryption and decryption
- Examples: AES, DES
-
Asymmetric-key cryptography: pair of keys (public for encryption, private for decryption)
- Examples: RSA, elliptic curve cryptography
Cryptographic Techniques
-
Block ciphers: divide plaintext into fixed-length blocks, encrypt each block
- Examples: AES, DES
-
Stream ciphers: encrypt plaintext one bit or byte at a time
- Examples: RC4, FISH
-
Hash functions: one-way encryption, produces fixed-length string (digest) from variable-length message
- Examples: SHA-256, MD5
- Digital signatures: asymmetric-key cryptography for sender authentication and message integrity
Cryptographic Attacks
- Brute force attack: try all possible keys to decrypt ciphertext
- Frequency analysis: analyze character frequency in ciphertext to deduce plaintext
- Side-channel attack: exploit implementation information, not the encryption algorithm itself
- Man-in-the-middle attack: intercept and alter communication between two parties
Cryptographic Protocols
- SSL/TLS: secure web browsing
- IPSec: secure network communication
- PGP: secure email communication
- SSH: secure remote access to computers
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Description
Learn about the practice of secure communication, encryption, and decryption techniques, as well as types of cryptography like symmetric-key and asymmetric-key cryptography.
