A
security protocol (
cryptographic protocol or
encryption protocol) is an abstract or concrete
protocolIn computing, a protocol is a set of rules which is used by computers to communicate with each other across a network. A protocol is a convention or standard that controls or enables the connection, communication, and data transfer between computing endpoints...
that performs a
securityInformation security means protecting information and information systems from unauthorized access, use, disclosure, disruption, modification or destruction.The terms information security, computer security and information assurance are...
-related function and applies cryptographic methods.
A protocol describes how the
algorithmIn mathematics, computing, linguistics, and related subjects, an algorithm is an effective method for solving a problem using a finite sequence of instructions. Algorithms are used for calculation, data processing, and many other fields....
s should be used. A sufficiently detailed protocol 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
security protocol (
cryptographic protocol or
encryption protocol) is an abstract or concrete
protocolIn computing, a protocol is a set of rules which is used by computers to communicate with each other across a network. A protocol is a convention or standard that controls or enables the connection, communication, and data transfer between computing endpoints...
that performs a
securityInformation security means protecting information and information systems from unauthorized access, use, disclosure, disruption, modification or destruction.The terms information security, computer security and information assurance are...
-related function and applies cryptographic methods.
A protocol describes how the
algorithmIn mathematics, computing, linguistics, and related subjects, an algorithm is an effective method for solving a problem using a finite sequence of instructions. Algorithms are used for calculation, data processing, and many other fields....
s should be used. A sufficiently detailed protocol 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
Authentication is the act of establishing or confirming something as authentic, that is, that claims made by or about the subject are true...
- Symmetric encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
and message authentication In cryptography, a key is a piece of information that determines the functional output of a cryptographic algorithm or cipher. Without a key, the algorithm would have no result. In encryption, a key specifies the particular transformation of plaintext into ciphertext, or vice versa during decryption...
material construction
- Secured application-level data transport
- Non-repudiation
Non-repudiation is the concept of ensuring that a party in a dispute cannot repudiate, or refute the validity of a statement or contract. Although this concept can be applied to any transmission, including television and radio, by far the most common application is in the verification and trust of...
methods
For example,
Transport Layer SecurityTransport Layer Security and its predecessor, Secure Sockets Layer , are cryptographic protocols that provide security for communications over networks such as the Internet...
(TLS) is a cryptographic protocol that is used to secure web (HTTP) connections. It has an entity authentication mechanism, based on the
X.509In cryptography, X.509 is an ITU-T standard for a public key infrastructure for single sign-on and Privilege Management Infrastructure...
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 different 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 exchangeDiffie-Hellman key exchange is a cryptographic protocol that allows two parties that have no prior knowledge of each other to jointly establish a shared secret key over an insecure communications channel...
, 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.
Cryptographic protocols can sometimes be
verified formallyIn the context of hardware and software systems, formal verification is the act of proving or disproving the correctness of intended algorithms underlying a system with respect to a certain formal specification or property, using formal methods of mathematics .- Usage :Formal verification can be...
on an abstract level.
Advanced cryptographic protocols
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.
Blind signaturesIn cryptography, a blind signature, as introduced by David Chaum , is a form of digital signature in which the content of a message is disguised before it is signed. The resulting blind signature can be publicly verified against the original, unblinded message in the manner of a regular digital...
can be used for
digital cashUsing cryptography, ecash was introduced by Gary Tilip with his partner, Stevhen Tigong of Bintulu, Sarawak as an anonymous electronic cash system. He used blind signatures to achieve unlinkability between withdrawal and spend transactions. Depending on the properties of the payment transactions,...
and
digital credentialsDigital credentials are meant to be the digital equivalent of paper based credentials. Just as an example a paper based credential could be a passport, a Driver's license, a membership certificate or some kind of ticket to obtain some service, like a cinema ticket or a public transport ticket...
to prove that a person holds an attribute or right without revealing that person's identity or the identities of parties that person transacted with.
Secure digital time-stampingTrusted timestamping is the process of securely keeping track of the creation and modification time of a document. Security here means that no one--not even the owner of the document--should be able to change it once it has been recorded provided that the timestamper's integrity is never...
can be used to prove that data (even if confidential) existed at a certain time.
Secure multiparty computationIn cryptography, secure multi-party computation is a problem that was initially suggested by Andrew C. Yao in a 1982 paper. In that publication, the millionaire problem was introduced: Alice and Bob are two millionaires who want to find out who is richer without revealing the precise amount of...
can be used to compute answers (such as determining the highest bid in an auction) based on confidential data (such as private bids), so that when the protocol is complete the participants know only their own input and the answer.
Undeniable signaturesUndeniable signatures are a form of digital signature invented by David Chaum and Hans van Antwerpen in 1989. They have two distinctive features,# The verification process is interactive, so that the signatory can limit who can verify the signature....
include interactive protocols that allow the signer to prove a forgery and limit who can verify the signature.
Deniable encryptionIn cryptography and steganography, deniable encryption is encryption that allows its users to convincingly deny the fact that the data is encrypted or, assuming that the data is obviously encrypted, its users can convincingly deny that they are able to decrypt it...
augments standard encryption by making it impossible for an attacker to mathematically prove the existence of a plaintext message.
Digital mixesAn anonymous remailer is a server computer which receives messages with embedded instructions on where to send them next, and which forwards them without revealing where they originally came from...
create hard-to-trace communications.
Examples
- Internet Key Exchange
Internet Key Exchange is the protocol used to set up a security association in the IPsec protocol suite. IKE uses a Diffie-Hellman key exchange to set up a shared session secret, from which cryptographic keys are derived...
- IPsec
Internet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a data stream. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of...
- Kerberos
- Point to Point Protocol
- Transport Layer Security
Transport Layer Security and its predecessor, Secure Sockets Layer , are cryptographic protocols that provide security for communications over networks such as the Internet...
External links