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There are two different meanings of the word cryptosystem. One is used by the cryptographic community, while the other is the meaning understood by the public. Image File history File links Key-crypto-sideways. ...

[edit] General meaning

In this meaning, the term cryptosystem is used as shorthand for "cryptographic system". A cryptographic system is any computer system that involves cryptography. Such systems include for instance, a system for secure electronic mail which might include methods for digital signatures, cryptographic hash functions, key management techniques, and so on. Cryptographic systems are made up of cryptographic primitives, and are usually rather complex. Because of this, breaking a cryptosystem is not restricted to breaking the underlying cryptographic algorithms - usually it is far easier to break the system as a whole, eg, through the not uncommon misconceptions of users in respect to the cryptosystem. To meet Wikipedias quality standards, this article may require cleanup. ... The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κρυπτός kryptós hidden, and the verb γράφω gráfo write) is the study of message secrecy. ... Wikipedia does not yet have an article with this exact name. ... In cryptography, a digital signature or digital signature scheme is a type of asymmetric cryptography used to simulate the security properties of a signature in digital, rather than written, form. ... In cryptography, a cryptographic hash function is a hash function with certain additional security properties to make it suitable for use as a primitive in various information security applications, such as authentication and message integrity. ... In cryptography, key management includes all of the provisions made in a cryptosystem design, in cryptographic protocols in that design, in user procedures, and so on, which are related to generation, exchange, storage, safeguarding, use, vetting, and replacement of keys. ... A Cryptographic primitives are well-established cryptographic routines that are frequently used in security-related topics. ...

[edit] Meaning in the context of cryptography

In this meaning, a cryptosystem refers to a suite of algorithms needed to implement a particular form of encryption and decryption. In mathematics, computing, linguistics, and related disciplines, an algorithm is a finite set of well-defined instructions for accomplishing some task which, given an initial state, will terminate in a defined end-state. ... “Cipher” redirects here. ... This article is about algorithms for encryption and decryption. ...

Typically, a cryptosystem consists of three algorithms: one for key generation, one for encryption, and one for decryption. The term cipher (sometimes cypher) is often used to refer to a pair of algorithms, one for encryption and one for decryption. Therefore, the term "cryptosystem" is most often used when the key generation algorithm is important. For this reason, the term "cryptosystem" is commonly used to refer to public key techniques; however both "cipher" and "cryptosystem" are used for symmetric key techniques. A key is a piece of information that controls the operation of a cryptography algorithm. ... Public key cryptography is a form of cryptography which generally allows users to communicate securely without having prior access to a shared secret key, by using a pair of cryptographic keys, designated as public key and private key, which are related mathematically. ... Symmetric-key algorithms are a class of algorithms for cryptography that use trivially related cryptographic keys for both decryption and encryption. ...

[edit] "Cryptographic system" vs. "cryptosystem"

The Internet Security Glossary RFC2828 dissuades from using the term "cryptosystem".

 $ cryptosystem (D) ISDs SHOULD NOT use this term as an abbreviation for cryptographic system. (For rationale, see: crypto.) 

 $ crypto (D) Except as part of certain long-established terms listed in this Glossary, ISDs SHOULD NOT use this abbreviated term because it may be misunderstood. Instead, use "cryptography" or "cryptographic".