🔍 Search
📥 Subscribe
Cryptography Cheat Sheet
Table of Contents
This cryptography cheat sheet provides a structured overview of modern cryptographic concepts, algorithms, protocols, and best practices for 2025. It is designed for developers, security professionals, and enthusiasts to quickly reference important information.
1. Fundamentals
Cryptography is the science of securing data and ensuring confidentiality, integrity, and authenticity. It includes both theoretical principles and practical techniques used to protect digital information.
| Topic | Description | Algorithm/Example |
|---|---|---|
| Symmetric Encryption | Uses the same key for both encryption and decryption. Fast and efficient for large data. | AES, DES |
| Asymmetric Encryption | To secure the communication, the public key is used for encryption and the private key is used for decryption. | RSA, ECC |
| Hashing | Converts data into a fixed-size string (digest) for integrity verification. | SHA-256, MD5 (deprecated) |
| Cryptographic Primitives | Basic building blocks such as random number generators and one-way functions. | HMAC, PRNG |
Symmetry in encryption relies on shared secrets, while asymmetry addresses key distribution challenges. Hashing ensures data integrity and is foundational to digital signatures.
2. Key Exchange
Key exchange protocols are necessary to securely share keys between parties over insecure channels. They prevent keys from being intercepted by adversaries.
| Topic | Description | Algorithm/Example |
|---|---|---|
| Diffie-Hellman | A method that allows two parties to generate a shared secret over an insecure channel. | DH Key Exchange |
| RSA Key Exchange | Uses public and private keys to securely exchange symmetric keys. | RSA-based key encapsulation |
| Elliptic Curve Diffie-Hellman (ECDH) | An efficient version using elliptic curves for short keys with high security. | ECDH |
| Post-Quantum Key Exchange | New protocols have been developed to resist attacks from quantum computers, which will ensure security in the future. | Lattice-based schemes |
Key exchange mechanisms are evolving, and post-quantum algorithms are becoming popular as quantum computing develops.
3. Encryption Modes
Encryption modes define how encryption algorithms process data blocks. They affect data security and error propagation in cipher operations.
| Topic | Description | Algorithm/Example |
|---|---|---|
| Electronic Codebook (ECB) | The simplest way; each block is encrypted independently, but the pattern may leak. | ECB mode in AES |
| Cipher Block Chaining (CBC) | Each block is XORed with the previous cipher block before encryption, which increases security. | CBC mode in AES |
| Counter (CTR) | Converts a block cipher to a stream cipher by encrypting the counter values. | CTR mode in AES |
| Galois/Counter Mode (GCM) | It provides both encryption and authentication, thereby preventing data tampering. | GCM mode in AES |
Encryption modes play a vital role in determining the security and performance of encryption schemes.
4. Digital Certificates
Digital certificates verify the identity of entities and secure communications using cryptography. They are issued by trusted certificate authorities (CAs).
| Topic | Description | Algorithm/Example |
|---|---|---|
| X.509 Certificates | A standard format for public key certificates used in SSL/TLS to secure websites and applications. | X.509 standard |
| Certificate Authorities (CA) | Trusted entities that issue and manage digital certificates verify ownership and authenticity. | Let's Encrypt, DigiCert |
| Public Key Infrastructure (PKI) | This framework manages keys and digital certificates, and ensures secure communications. | PKI frameworks |
| Certificate Revocation Lists (CRL) | List of revoked certificates before expiration, which increases trust. | CRL in PKI systems |
Digital certificates build trust in online communications. They are important for securing transactions and authenticating websites.
5. Protocols
Protocols use cryptography to establish secure communication channels. They define rules for encryption, authentication, and data integrity in the network.
| Topic | Description | Algorithm/Example |
|---|---|---|
| TLS/SSL | Secure protocol for encrypting communications over the Internet and protecting data in transit. | TLS 1.3, SSL (older version) |
| IPsec | Group of protocols that ensure secure IP communications through authentication and encryption. | IPsec VPNs |
| SSH | The Secure Shell protocol is used for encrypted remote server access and data tunneling. | OpenSSH |
| HTTPS | HTTP over TLS/SSL ensures secure browsing by encrypting website communications. | HTTPS websites |
These protocols are the backbone of secure communications in today's digital world. They are constantly updated to address new vulnerabilities.
6. Best Practices
Adopting best practices in cryptography ensures strong security and reduces the risk of vulnerabilities. These guidelines are a must for cybersecurity professionals and ethical hackers.
| Topic | Description | Algorithm/Example |
|---|---|---|
| Use Strong Keys | Always use long and random keys to improve the strength of encryption. | 256-bit keys in AES |
| Regular Key Rotation | Replace keys regularly to limit potential damage from damaged keys. | Automated key management tools |
| Secure Key Storage | Use a hardware security module (HSM) or secure vault to securely store cryptographic keys. | HSM devices, Key Vault |
| Update Cryptographic Libraries | Keep libraries and algorithms updated to mitigate emerging vulnerabilities. | OpenSSL, BouncyCastle |
Following these practices helps maintain the integrity and confidentiality of encrypted data. They also support compliance with industry standards.
7. Common Attacks
Understanding common attacks on cryptographic systems is important for both defense and ethical hacking. These attacks exploit vulnerabilities in algorithms or implementations.
| Topic | Description | Algorithm/Example |
|---|---|---|
| Brute Force Attacks | Tries to guess the keys by trying all possible combinations until the correct key is found. | Exhaustive search on AES keys |
| Man-in-the-Middle (MitM) | Intercepting and possibly altering communications between two parties without their knowledge. | MitM in TLS sessions |
| Side-Channel Attacks | Uses physical implementation (time, power consumption) to extract cryptographic keys. | Timing attacks on RSA |
| Replay Attacks | This involves capturing and reusing legitimate data transmissions to deceive the recipient. | Replayed authentication tokens |
By learning these attack methods, professionals can design systems that are more resistant to vulnerabilities and improve incident response plans.
8. Cryptography Tools
There are a variety of tools available for testing, analyzing, and implementing cryptographic measures. They are widely used in cybersecurity assessments and ethical hacking.
| Topic | Description | Algorithm/Example |
|---|---|---|
| OpenSSL | A robust toolkit for Secure Sockets Layer (SSL) and Transport Layer Security (TLS) implementations. | OpenSSL command-line tools |
| Wireshark | Network protocol analyzer that can capture and dissect secure traffic for analysis. | Packet capture in Wireshark |
| Metasploit Framework | A penetration testing tool with modules to exploit cryptographic vulnerabilities. | Metasploit modules |
| Hashcat | An advanced password recovery tool used to test the strength of a hash function through brute force methods. | Hashcat for cracking hashes |
These tools are essential in both defensive security and ethical hacking to analyze systems and identify vulnerabilities.
9. Regulations
Cryptographic practices must comply with legal and regulatory requirements. Compliance with these regulations is crucial to protect sensitive data and avoid legal penalties.
| Topic | Description | Algorithm/Example |
|---|---|---|
| GDPR | European regulation ensures data protection and privacy, and influences the use of encryption for personal data. | GDPR-compliant encryption |
| HIPAA | US regulation that sets standards for protecting sensitive health information through encryption. | HIPAA-compliant systems |
| FIPS 140-3 | US government standard for validating cryptographic modules, ensuring they meet high security standards. | FIPS-validated cryptographic modules |
| NIST Guidelines | Provides best practices and standards for cryptography used across industries for secure communications. | NIST SP 800 series |
Regulations ensure that organizations implement strong cryptographic measures. They also standardize practices to help protect sensitive information.
10. Emerging Trends
The field of cryptography is evolving rapidly. New trends are emerging to tackle advanced threats and leverage innovative technologies for stronger security.
| Topic | Description | Algorithm/Example |
|---|---|---|
| Post-Quantum Cryptography | Development of algorithms designed to be secure against quantum computer attacks. | NTRU, CRYSTALS-Kyber |
| Blockchain and Distributed Ledger Technologies | Use cryptographic principles to ensure transparency and security in decentralized systems. | Bitcoin's SHA-256, Ethereum |
| Homomorphic Encryption | This allows calculations to be performed on encrypted data without decrypting it, thereby maintaining confidentiality. | BFV, CKKS schemes |
| Zero-Knowledge Proofs | A method which enables a party to prove knowledge of a fact without disclosing the fact. | zk-SNARKs, zk-STARKs |
Emerging trends in cryptography aim to combat new challenges such as quantum threats and emerging cyber attacks. These innovations are expected to shape the future of secure communications and data processing.
Use this cheat sheet as a quick reference to refresh your knowledge and guide your implementation of cryptographic solutions.
Remember that cryptography is a complex topic, so be sure to understand each concept thoroughly to increase your knowledge and proficiency in this important field.