An Introduction to Cryptography

Cryptography Glossary

This glossary provides definitions for common terms used in the field of cryptography. Understanding these terms is crucial for grasping the concepts discussed throughout this website. For a deeper dive into how these concepts apply in other tech areas, you might explore Data Structures Explained (Python).

Algorithm

A precise sequence of instructions or a set of rules to be followed in calculations or other problem-solving operations, especially by a computer. In cryptography, an algorithm (or cipher) dictates how encryption and decryption are performed.

Asymmetric Encryption (Public-Key Cryptography)

A cryptographic system that uses pairs of keys: public keys, which may be disseminated widely, and private keys, which are known only to the owner. Used for tasks like encryption and digital signatures. Learn more on our Asymmetric Encryption page.

Authentication

The process of verifying the identity of a user, device, or message. It ensures that a party is who or what it claims to be.

Avalanche Effect

A desirable property of cryptographic algorithms, where a small change in the input (e.g., flipping a single bit in the plaintext or key) results in a significant change in the output (e.g., about half the bits in the ciphertext change). This is crucial for hashing functions.

Block Cipher

A type of symmetric encryption algorithm that encrypts a fixed-size block of data (e.g., 128 bits) at a time. Examples include AES and DES.

Brute-Force Attack

An attack method that involves systematically checking all possible keys or passwords until the correct one is found. The feasibility of this attack depends on the key length and available computing power.

Caesar Cipher

One of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. Mentioned in our History of Cryptography.

Cipher

An algorithm for performing encryption or decryption. It's a set of steps used to transform plaintext into ciphertext and vice versa.

Ciphertext

The encrypted form of a message, rendered unreadable to unauthorized parties.

Collision (Hash)

In hashing functions, a collision occurs when two different inputs produce the same hash output. Strong hash functions are designed to be collision-resistant.

Cryptanalysis

The study of methods for obtaining the meaning of encrypted information, without access to the secret key normally required to do so. Essentially, code breaking.

Cryptography

The practice and study of techniques for secure communication in the presence of third parties (adversaries). It encompasses methods for encryption, decryption, hashing, and digital signatures. See our Introduction.

Cryptographic Key (Key)

A piece of information (a parameter) that determines the functional output of a cryptographic algorithm. For encryption algorithms, a key specifies the transformation of plaintext into ciphertext, and vice versa for decryption.

Data Integrity

The assurance that digital information is uncorrupted and has not been altered, either accidentally or maliciously. Hashing functions and digital signatures are key to maintaining data integrity.

Decryption

The process of converting ciphertext back into its original, readable form (plaintext) using a key.

Digital Signature

A mathematical scheme for verifying the authenticity of digital messages or documents. It provides authenticity, integrity, and non-repudiation. Explore more on our Digital Signatures page.

Encryption

The process of converting information or data (plaintext) into a code (ciphertext), especially to prevent unauthorized access.

End-to-End Encryption (E2EE)

A system of communication where only the communicating users can read the messages. In E2EE, no third party, not even the service provider (e.g., messaging app company), can access the cryptographic keys needed to decrypt the conversation.

Hash Function

A function that converts an input of arbitrary length into a fixed-size string of characters, which is the hash value. Cryptographic hash functions have specific properties like pre-image resistance and collision resistance. Details on our Hashing Functions page.

Key Exchange (Key Agreement)

A method in cryptography by which cryptographic keys are exchanged between two parties, allowing use of a cryptographic algorithm. Diffie-Hellman is a common key exchange algorithm.

Key Length (Key Size)

The size of a cryptographic key, measured in bits. Longer keys generally provide stronger security against brute-force attacks.

Non-Repudiation

Assurance that someone cannot deny the validity of something. Digital signatures provide non-repudiation, meaning the sender cannot deny having sent a message they signed.

Plaintext

The original, unencrypted message or data that is readable and understandable.

Private Key

In asymmetric cryptography, the secret key of a key pair that is kept confidential by its owner. Used for decryption or creating digital signatures.

Public Key

In asymmetric cryptography, the publicly available key of a key pair. Used for encryption or verifying digital signatures.

Public Key Infrastructure (PKI)

A set of roles, policies, hardware, software, and procedures needed to create, manage, distribute, use, store, and revoke digital certificates and manage public-key encryption.

Salt

Random data that is used as an additional input to a one-way function that hashes data, typically a password. Salts defend against dictionary attacks and pre-computed rainbow table attacks.

Stream Cipher

A type of symmetric encryption algorithm that encrypts data one bit or byte at a time. Examples include RC4 (though now insecure).

Symmetric Encryption (Secret-Key Cryptography)

A cryptographic system where the same key is used for both encryption and decryption. Read more on our Symmetric Encryption page.

This glossary is a starting point. The field of cryptography is vast and continually evolving, with new terms and concepts emerging regularly. Stay updated by exploring resources like AI & Machine Learning Basics which often intersect with modern cryptographic applications.