Key/Config-authentication is used to solve the problem of authenticating the keys of the person (say "person B") to some other person ("person A") is talking to or trying to talk to. In other words, it is the process of assuring that the key of "person A" held by "person B" does in fact belong to "person A" and vice versa. This is usually done after the keys have been shared among the two sides over some secure channel. However, some algorithms share the keys at the time of authentication. The simplest solution for this kind of problem is for the two concerned users to communicate and exchange keys. However, for systems in which there are a large number of users or in which the users do not personally know each other (e.g., Internet shopping), this is not practical. There are various algorithms for both symmetric keys and asymmetric public key cryptography to solve this problem.

Authentication using Shared Keys

For key authentication using the traditional

symmetric key Symmetric-key algorithms are algorithms for cryptography that use the same cryptographic keys for both the encryption of plaintext and the decryption of ciphertext. The keys may be identical, or there may be a simple transformation to go between t ...

cryptography, this is the problem of assuring that there is no

man-in-the-middle attack In cryptography and computer security, a man-in-the-middle, monster-in-the-middle, machine-in-the-middle, monkey-in-the-middle, meddler-in-the-middle, manipulator-in-the-middle (MITM), person-in-the-middle (PITM) or adversary-in-the-middle (AiTM) ...

er who is trying to read or spoof the communication. There are various algorithms used now-a-days to prevent such attacks. The most common among the algorithms are

Diffie–Hellman key exchange Diffie–Hellman key exchangeSynonyms of Diffie–Hellman key exchange include: * Diffie–Hellman–Merkle key exchange * Diffie–Hellman key agreement * Diffie–Hellman key establishment * Diffie–Hellman key negotiation * Exponential key exc ...

, authentication using

Key distribution center {{cleanup, date=November 2011 In cryptography, a key distribution center (KDC) is part of a cryptosystem intended to reduce the risks inherent in exchanging keys. KDCs often operate in systems within which some users may have permission to use ce ...

, kerberos and Needham–Schroeder protocol. Other methods that can be used include Password-authenticated key agreement protocols etc.

Authentication using Public Key Cryptography

Crypto systems using

asymmetric key Public-key cryptography, or asymmetric cryptography, is the field of cryptographic systems that use pairs of related keys. Each key pair consists of a public key and a corresponding private key. Key pairs are generated with cryptographic alg ...

algorithms do not evade the problem either. That a public key can be known by all without compromising the security of an encryption algorithm (for some such algorithms, though not for all) is certainly useful, but does not prevent some kinds of attacks. For example, a spoofing attack in which public key ''A'' is claimed publicly to be that of user Alice, but is in fact a public key belonging to

Mallet A mallet is a tool used for imparting force on another object, often made of rubber or sometimes wood, that is smaller than a maul or beetle, and usually has a relatively large head. The term is descriptive of the overall size and propor ...

, is easily possible. No public key is inherently bound to any particular user, and any user relying on a defective binding (including Alice herself when she sends herself protected messages) will have trouble. The most common solution to this problem is the use of

public key certificate In cryptography, a public key certificate, also known as a digital certificate or identity certificate, is an electronic document used to prove the validity of a public key. The certificate includes information about the key, information about t ...

s and certificate authorities (CAs) for them in a

public-key infrastructure A public key infrastructure (PKI) is a set of roles, policies, hardware, software and procedures needed to create, manage, distribute, use, store and revoke digital certificates and manage public-key encryption. The purpose of a PKI is to facili ...

(PKI) system. The

certificate authority In cryptography, a certificate authority or certification authority (CA) is an entity that stores, signs, and issues digital certificates. A digital certificate certifies the ownership of a public key by the named subject of the certificate. Thi ...

(CA) acts as a 'trusted third party' for the communicating users and, using cryptographic binding methods (e.g.,

digital signature A digital signature is a mathematical scheme for verifying the authenticity of digital messages or documents. A valid digital signature, where the prerequisites are satisfied, gives a recipient very high confidence that the message was created b ...

s) represents to both parties involved that the public keys each holds which allegedly belong to the other, actually do so. A digital notary service, if you will. Such CAs can be private organizations providing such assurances, or government agencies, or some combination of the two. However, in a significant sense, this merely moves the key authentication problem back one level for any CA may make a good faith certification of some key but, through error or malice, be mistaken. Any reliance on a defective key certificate 'authenticating' a public key will cause problems. As a result, many people find all PKI designs unacceptably insecure. Accordingly, key authentication methods are being actively researched.

References

{{reflist

External links

Honest Achmed asks for trust

Kerberos: The Network Authentication Protocol

Kerberos Authentication explained
Key management

Authentication using Shared Keys

Authentication using Public Key Cryptography

See also

References

External links