Introduction to Cryptography
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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

<p>encryption</p> Signup and view all the answers

Digital signatures use ______ cryptography to authenticate and ensure integrity of messages

<p>asymmetric</p> Signup and view all the answers

______ is ensuring data is not tampered with or altered

<p>Integrity</p> Signup and view all the answers

A ______-plaintext attack is accessing both the encrypted and decrypted data

<p>Known</p> Signup and view all the answers

HTTPS is an example of a secure online ______ that uses cryptography

<p>transaction</p> Signup and view all the answers

What is the main goal of cryptography?

<p>To provide confidentiality, integrity, and authenticity of messages.</p> Signup and view all the answers

Describe the difference between symmetric-key and asymmetric-key cryptography.

<p>Symmetric-key cryptography uses the same key for both encryption and decryption, while asymmetric-key cryptography uses a pair of keys: a public key for encryption and a private key for decryption.</p> Signup and view all the answers

What is a block cipher and how does it operate?

<p>A block cipher divides plaintext into fixed-length blocks and encrypts each block independently.</p> Signup and view all the answers

What are digital signatures used for in cryptography?

<p>Digital signatures are used to authenticate the sender and ensure the integrity of the message.</p> Signup and view all the answers

Explain what a brute force attack entails in cryptographic terms.

<p>A brute force attack involves trying all possible keys to decrypt ciphertext until the correct key is found.</p> Signup and view all the answers

What is meant by the term 'ciphertext'?

<p>Ciphertext is the encrypted message or data that is unreadable without the decryption key.</p> Signup and view all the answers

Define what a hash function does in the context of cryptography.

<p>A hash function produces a fixed-length string of characters (digest) from a variable-length message.</p> Signup and view all the answers

What is a man-in-the-middle attack?

<p>A man-in-the-middle attack involves intercepting and altering the communication between two parties.</p> Signup and view all the answers

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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Learn about the practice of secure communication, encryption, and decryption techniques, as well as types of cryptography like symmetric-key and asymmetric-key cryptography.

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