Cryptography is the backbone of secure digital communication. It transforms readable messages into secret code and back again, ensuring only intended recipients can access the information. This process involves encryption, decryption, and various key systems.
Cryptography provides essential properties for secure communication: confidentiality, integrity, authentication, and non-repudiation. These concepts work together to protect data, verify identities, and ensure the trustworthiness of digital interactions in our interconnected world.
Encryption and Decryption
Encryption and Decryption Processes
- Encryption converts plaintext into ciphertext using a cryptographic key to protect the confidentiality of the original message
- Decryption reverses the encryption process by converting ciphertext back into plaintext using the appropriate cryptographic key
- Plaintext refers to the original, unencrypted message or data that is readable and understandable without any special processing
- Ciphertext is the encrypted version of the plaintext that appears as scrambled or unreadable characters to protect the original message
Symmetric and Asymmetric Encryption
- Symmetric encryption uses the same cryptographic key for both encrypting and decrypting data
- The key must be securely shared between the sender and receiver beforehand
- Symmetric encryption is generally faster and more efficient than asymmetric encryption (AES, DES)
- Asymmetric encryption, also known as public-key cryptography, uses a pair of keys: a public key for encryption and a private key for decryption
- The public key can be freely distributed, while the private key must be kept secret by the owner
- Asymmetric encryption provides better security for key exchange and digital signatures (RSA, ECC)
- A cryptographic key is a string of bits used by the encryption algorithm to transform plaintext into ciphertext and vice versa
- The security of the encrypted data depends on the secrecy and strength of the key
- Key management, including generation, distribution, and storage, is crucial for maintaining the security of the encryption system
Cryptographic Properties
Confidentiality and Integrity
- Confidentiality ensures that the information is accessible only to authorized parties and remains secret from unauthorized entities
- Encryption is a primary means of achieving confidentiality by protecting data from unauthorized access (end-to-end encryption in messaging apps)
- Integrity guarantees that the information has not been altered, tampered with, or corrupted during storage or transmission
- Cryptographic hash functions and digital signatures are used to verify the integrity of data (SHA-256 for verifying file downloads)
Authentication and Non-Repudiation
- Authentication verifies the identity of the sender or the origin of the information
- Digital signatures and message authentication codes (MACs) are used to authenticate the source of data (digital certificates for website authentication)
- Non-repudiation prevents an entity from denying their involvement in a transaction or communication
- Digital signatures provide non-repudiation by ensuring that the signer cannot deny having signed the message (legally binding digital contracts)
- Cryptographic techniques, such as digital signatures and timestamping, are employed to achieve authentication and non-repudiation in various applications (secure email, financial transactions)