A cryptographic protocol is an abstract or concrete protocol that performs a security-related function and applies cryptographic methods, often as sequences of cryptographic primitives. A protocol describes how the algorithms should be used and includes details about data structures and representations, at which point it can be used to implement multiple, interoperable versions of a program.
Cryptographic protocols are widely used for secure application-level data transport. A cryptographic protocol usually incorporates at least some of these aspects:
Key agreement or establishment
Entity authentication
Symmetric encryption and message authentication material construction
Secured application-level data transport
Non-repudiation methods
Secret sharing methods
Secure multi-party computation
For example, Transport Layer Security (TLS) is a cryptographic protocol that is used to secure web (HTTPS) connections. It has an entity authentication mechanism, based on the X.509 system; a key setup phase, where a symmetric encryption key is formed by employing public-key cryptography; and an application-level data transport function. These three aspects have important interconnections. Standard TLS does not have non-repudiation support.
There are other types of cryptographic protocols as well, and even the term itself has various readings; Cryptographic application protocols often use one or more underlying key agreement methods, which are also sometimes themselves referred to as "cryptographic protocols". For instance, TLS employs what is known as the Diffie–Hellman key exchange, which although it is only a part of TLS per se, Diffie–Hellman may be seen as a complete cryptographic protocol in itself for other applications.
A wide variety of cryptographic protocols go beyond the traditional goals of data confidentiality, integrity, and authentication to also secure a variety of other desired characteristics of computer-mediated collaboration.
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This course introduces the basics of cryptography. We review several types of cryptographic primitives, when it is safe to use them and how to select the appropriate security parameters. We detail how
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Cryptography, or cryptology (from κρυπτός "hidden, secret"; and γράφειν graphein, "to write", or -λογία -logia, "study", respectively), is the practice and study of techniques for secure communication in the presence of adversarial behavior. More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages. Modern cryptography exists at the intersection of the disciplines of mathematics, computer science, information security, electrical engineering, digital signal processing, physics, and others.
In cryptography, Camellia is a symmetric key block cipher with a block size of 128 bits and key sizes of 128, 192 and 256 bits. It was jointly developed by Mitsubishi Electric and NTT of Japan. The cipher has been approved for use by the ISO/IEC, the European Union's NESSIE project and the Japanese CRYPTREC project. The cipher has security levels and processing abilities comparable to the Advanced Encryption Standard. The cipher was designed to be suitable for both software and hardware implementations, from low-cost smart cards to high-speed network systems.
In cryptography, a key-agreement protocol is a protocol whereby two or more parties can agree on a cryptographic key in such a way that both influence the outcome. If properly done, this precludes undesired third parties from forcing a key choice on the agreeing parties. Protocols that are useful in practice also do not reveal to any eavesdropping party what key has been agreed upon. Many key exchange systems have one party generate the key, and simply send that key to the other party—the other party has no influence on the key.
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