Clear DefinitionsCipher
1 min read
Pronunciation
[sahy-fer]
Analogy
A cipher is like a complex recipe for transforming readable text into coded gibberish and back again. Just as a recipe specifies exact ingredients and steps to create a dish, a cipher defines precise mathematical operations for transforming data. And just as you need the complete recipe to recreate the dish, you need the cipher algorithm and the correct key to decrypt the message.
Definition
An algorithm for performing encryption or decryption—a series of steps that converts plaintext to ciphertext or vice versa. Ciphers form the foundation of cryptographic security in blockchain systems by protecting sensitive data and communications.
Key Points Intro
Ciphers provide the mathematical foundation for securing blockchain data and communications.
Key Points
Transforms readable plaintext into encrypted ciphertext and vice versa.
Requires both the algorithm and the correct key to decrypt successfully.
Categories include block ciphers (processing fixed-size blocks) and stream ciphers (processing continuous data).
Modern ciphers rely on complex mathematics rather than secrecy of the algorithm.
Example
When a hardware wallet communicates with a blockchain application, it often uses ciphers like AES-256 to encrypt the transaction details during transmission, protecting them from potential eavesdroppers while ensuring only authorized participants can decrypt and process the information.
Technical Deep Dive
Cryptographic ciphers fall into two primary categories: (1) Block ciphers process fixed-size data blocks (typically 64, 128, or 256 bits), applying substitution and permutation networks to thoroughly mix the data with key-derived values. Examples include AES, 3DES, and Blowfish. Block ciphers operate in various modes including ECB (Electronic Codebook), CBC (Cipher Block Chaining), CTR (Counter), and GCM (Galois/Counter Mode), each with different security and performance characteristics. (2) Stream ciphers generate a pseudorandom keystream that's combined with plaintext (typically using XOR operations) to produce ciphertext. Examples include ChaCha20 and the older RC4. Modern blockchain implementations typically use authenticated encryption, combining ciphers with integrity protection through mechanisms like HMAC or GMAC. Public-key cryptography systems like RSA and ECC are technically asymmetric ciphers, though they're often categorized separately from symmetric ciphers due to their different mathematical foundations and use cases.
Security Warning
Never implement custom ciphers for production systems—use established, well-vetted implementations from reputable cryptographic libraries. Additionally, cipher security depends heavily on proper mode selection, key management, and initialization vector handling. Even a strong cipher can be compromised by implementation errors.
Caveat
While ciphers provide confidentiality protection, they don't inherently provide authentication or integrity verification. For complete security, ciphers should be combined with mechanisms like message authentication codes or digital signatures, as is common in properly designed blockchain security systems.
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