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Topic: Keyed hash message authentication code


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In the News (Mon 1 Dec 08)

  
  Cryptographic hash function - Wikipedia, the free encyclopedia
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.
A message authentication code or MAC takes a message and a secret key and generates a "MAC tag", such that it is difficult for an attacker to generate a valid (message, tag) pair that doesn't match one they've already seen; they are used to prevent attackers forging messages, among other uses.
Such file hashes are often the top hash of a hash list or a hash tree which allows for additional benefits.
en.wikipedia.org /wiki/Cryptographic_hash_function   (1431 words)

  
 hmac   (Site not responding. Last check: 2007-10-08)
A keyed-hash message authentication code, or HMAC, is a type of message authentication code (MAC) calculated using a cryptographic hash function in combination with a secret key.
As with any MAC, it may be used to simultaneously verify both the data integrity and the authenticity of a message.
Any iterative cryptographic hash function, e.g., SHA-1, RIPEMD-160, may be used in the calculation of an HMAC; the cryptographic strength of the HMAC depends upon the cryptographic strength of the underlying hash function and on the size and quality of the key.
www.yourencyclopedia.net /HMAC.html   (191 words)

  
 HMAC - Wikipedia, the free encyclopedia
Any iterative cryptographic hash function, such as MD5 or SHA-1, may be used in the calculation of an HMAC; the resulting MAC algorithm is termed HMAC-MD5 or HMAC-SHA-1 accordingly.
The cryptographic strength of the HMAC depends upon the cryptographic strength of the underlying hash function and on the size and quality of the key.
where h is an iterated hash function, K is a secret key padded with extra zeros to the block size of the hash function and m is the message to be authenticated.
en.wikipedia.org /wiki/HMAC   (376 words)

  
 Message authentication code   (Site not responding. Last check: 2007-10-08)
The purpose of the code is to ensure the authenticity aswell as the integrity of a message in transit.
The Message Authentication Code (MAC) is an ANSI standard for a shortstring of information used to authenticate a message which is based on DES, and is also known as the Data AuthenticationCode.
Message digests (or the output from cryptographic hash functions) were formerly widelyused for the purpose of providing a message integrity check, but the message authentication code construction resolved somesecurity problems and so is now preferred.
www.therfcc.org /message-authentication-code-72569.html   (187 words)

  
 [No title]
Definition of HMAC The definition of HMAC requires a cryptographic hash function, which we denote by H, and a secret key K. We assume H to be a cryptographic hash function where data is hashed by iterating a basic compression function on blocks of data.
Keys The key for HMAC can be of any length (keys longer than B bytes are first hashed using H).
Keys longer than L bytes are acceptable but the extra length would not significantly increase the function strength.
www.ietf.org /rfc/rfc2104.txt   (2246 words)

  
 BioMed Central | Full text | Some methods for blindfolded record linkage   (Site not responding. Last check: 2007-10-08)
Messages containing identifying information from many sources are mixed by the proxy and delayed by random amounts before being forwarded to the central linkage bureau, thus obfuscating the source of each message.
A one-way hash function, such as the Secure Hash Algorithm (SHA) [22], transforms a string or other series of bytes into a new, fixed-length string (a hash value) in such as way that it is impossible, or at least extremely difficult, to discover the value of the original string from the hash value.
Although Carol is unable to reverse the hashing process and discover the original values, she is able to mount a dictionary attack against the list of hashes which she receives from Alice and Bob [24].
www.biomedcentral.com /1472-6947/4/9   (10902 words)

  
 Privacy, Modified - De-Identification of PHI
Based on the Department's intent that the re- identification code not be considered one of the enumerated identifiers that must be excluded under the safe harbor for de-identification, and the public comment supporting this clarification, the Department adopts the provision as proposed.
It is not solely the public's access to the key that matters for these purposes; the covered entity may not share the key to the re- identification code with anyone, including the recipient of the data, regardless of whether the intent is to facilitate re-identification or not.
The 17 restricted zip codes are: 036, 059, 063, 102, 203, 556, 692, 790, 821, 823, 830, 831, 878, 879, 884, 890, and 893.
www.hipaadvisory.com /regs/finalprivacymod/deid.htm   (2032 words)

  
 Gucci Key   (Site not responding. Last check: 2007-10-08)
Keyed-hash message authentication code A keyed-hash message authentication code, or HMAC, is a type of message authentication code (MAC) calculated using a cryptographic hash function in combination with a secret key.
Key escrow Key escrow is a controversial arrangement where the keys needed to decrypt encrypted data must be held in escrow by a third party so that government agencies can obtain them to decrypt messages which they suspect to be relevant to national security.
Key field A key field is a field of a database (typically a relational database) table which together form a unique identifier for a record (a table entry).
www.bosale.com /Gucci+Key.html   (283 words)

  
 Introduzione   (Site not responding. Last check: 2007-10-08)
Data origin authentication service provides verification that the identity of the original source of a received data unit is as claimed; there can be no such verification if the data unit has been altered.
Peer entity authentication service provides verification that the identity of a peer entity in a current association is as claimed; there can be no such verification if the claimed identity has been altered.
Unlike peer entity authentication service, this service is independent of any association between the originator and the recipient, and the data in question may have originated at any time in the past.
almecfurniture.com /documenti/sicurezza/rfc2828/da-de.html   (1184 words)

  
 [ Ant ] D ◁ GIST ◁ Glossaries ◁ Overview ◁ Security Matters
Each person uses their own private key and the other person’s public key to compute a key, k, that, because of the mathematics of the algorithm, is the same for each of them.
or cryptographic key, unless the context is insufficient to distinguish the digital key from another kind of key, such as a metal key for a door lock.
Data appended to a message, that allow the recipient of the message to verify the source and integrity of the message.
homepage.mac.com /antallan/gistd.html   (5030 words)

  
 RFC 2104 (rfc2104) - HMAC: Keyed-Hashing for Message Authentication
In particular, hash functions that perform well in software, and for which code is freely and widely available.
The authentication key K can be of any length up to B, the block length of the hash function.
Message authentication, as opposed to encryption, has a "transient" effect.
www.faqs.org /rfcs/rfc2104.html   (2179 words)

  
 ipedia.com: Cryptographic hash function Article   (Site not responding. Last check: 2007-10-08)
A hash function takes a long string (or message) of any length as input and produces a fixed length string as output; not all such are suitable for use in cryptography.
In contrast, message authentication codes are keyed hash functions; only the owner of a secret key can compute hashes with that key.
Hash functions can also be used in the generation of pseudorandom bits, if they meet some additional, statistical, tests.
www.ipedia.com /cryptographic_hash_function.html   (1112 words)

  
 [No title]
HMAC is a hash function based message authentication code that was designed to meet the requierments of the IPSEC working group in the IETF, and is now a standard.
The main technical paper on the subject, containing the formal security analysis, is Keying hash functions for message authentication.
Moreover they use the hash function (or its compression function) as a fl box, so that widely available library code or hardware can be used to implement them in a simple way, and replaceability of the underlying hash function is easily supported.
www.cs.ucsd.edu /users/mihir/papers/hmac.html   (483 words)

  
 [No title]
It provides mechanisms to disseminate group policy and authenticate users, rules to perform access control decisions during group establishment and recovery, capabilities to recover from the compromise of group members, delegation of group security functions, and capabilities to destroy the group.
In particular, this variant deploys the classic Diffie-Hellman key agreement protocol for key establishment featuring perfect forward secrecy in conjunction with a keyed hash message authentication code for achieving mutual authentication and message integrity of the key management messages exchanged.
This document specifies a group key distribution protocol (GKDP) based on IKEv2, the IPsec key management protocol; the new protocol is similar to IKEv2 in message and payload formats, and message semantics to a large extent.
www.ietf.org /ids.by.wg/msec.html   (994 words)

  
 FIPS for Keyed-Hash Message Authentication Code (HMAC)
Message authentication is achieved via the construction of a message authentication code (MAC).
The receiver computes the MAC on the received message using the same key and HMAC function as was used by the originator, and compares the result computed with the received MAC.
If the two values match, the message has been correctly received, and the receiver is assured that the message originator is a member of the community of users that share the key.
ftp.die.net /mirror/cryptome/nist010501.htm   (556 words)

  
 HMAC -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-08)
Any iterative cryptographic hash function, such as (Click link for more info and facts about MD5) MD5 or (Click link for more info and facts about SHA-1) SHA-1, may be used in the calculation of an HMAC; the resulting MAC algorithm is termed HMAC-MD5 or HMAC-SHA-1 accordingly.
Mihir Bellare, Ran Canetti and Hugo Krawczyk, Keying Hash Functions for Message Authentication, CRYPTO 1996, pp1–15.
Mihir Bellare, Ran Canetti and Hugo Krawczyk, Message authentication using hash functions: The HMAC construction, CryptoBytes 2(1), Spring 1996.
www.absoluteastronomy.com /encyclopedia/h/hm/hmac3.htm   (400 words)

  
 Keyed-hash message authentication code   (Site not responding. Last check: 2007-10-08)
SHA-1 RIPEMD-160 may be used in the calculation an HMAC; the cryptographic strength of the depends upon the cryptographic strength of the hash function and on the size and of the key.
The construction and analysis of HMACs was published in 1996 by Mihir Bellare Ran and Hugo Krawczyk who also wrote RFC 2104.
As a person interested in bible codes and all I found this a great way to get insight into what the bible codes really mean.
www.freeglossary.com /Keyed-hash_message_authentication_code   (442 words)

  
 Keyed-hash message authentication code   (Site not responding. Last check: 2007-10-08)
The construction and analysis of HMACs was first published in 1996 by Mihir Bellare, Ran Canetti, and Hugo Krawczyk, who also authored RFC 2104.
RFC 2104, "HMAC: Keyed-Hashing for Message Authentication'', http://www.ietf.org/rfc/rfc2104.txt
FIPS PUB 198, The Keyed-Hash Message Authentication Code, http://csrc.nist.gov/publications/fips/fips198
www.bopedia.com /en/wikipedia/k/ke/keyed_hash_message_authentication_code.html   (154 words)

  
 RE: [courtfiling-process] Security of court orders
The "hash total" to which Jim refers is an electronic signature.
A key is required to calculate the electronic signature.
For very large documents this can be much more efficient than securing a key or key pair or constantly downloading copies of the original document.
www.oasis-open.org /archives/courtfiling-process/200304/msg00014.html   (944 words)

  
 Authentication   (Site not responding. Last check: 2007-10-08)
The simplest solution for this problem is for the two users to meet face-to-face and exchange keys, however for systems where there are a large amount of users or the users do not know each other (for example with internet shopping) this is not practical.
Two factor authentication is a security process that confirms user identities using two distinctive factors - a password and a personalized item, usually a one time number generating device or smart card.
Message authentication code A Message authentication code (MAC) is a one way hash function which takes as input both 1000 a symmetric key and some data.
bonose.com /Authentication.html   (586 words)

  
 Citations: RFC 2104: HMAC: Keyed-Hashing for Message Authentication - Krawczyk, Bellare, Canetti (ResearchIndex)   (Site not responding. Last check: 2007-10-08)
Citations: RFC 2104: HMAC: Keyed-Hashing for Message Authentication - Krawczyk, Bellare, Canetti (ResearchIndex)
A Message Authentication Code is a cryptographic hash of a message concatenated with a key.
based on the SHA 1 hash function [18] The pseudorandom function is the same function by which the message authentication code is computed, with a full length output.
citeseer.ist.psu.edu /context/1517077/0   (584 words)

  
 [Exim] Matching bounce recipients against sender hashes   (Site not responding. Last check: 2007-10-08)
you include some uniquifying data (the message ID in this case) in the address, and you protect it from forgery using an HMAC signature (keyed-hash message authentication code).
A fortnight is probably a good period to use, and anything less than a week is likely to be too short.
This is more difficult because Exim doesn't have a base 62 decode expansion operator to get the time out of the message ID, or a string less-than comparison operator for comparing base 62 encoded times.
www.exim.org /pipermail/exim-users/Week-of-Mon-20040607/072692.html   (211 words)

  
 Authentication in TutorGig Encyclopedia   (Site not responding. Last check: 2007-10-08)
A further paper proposed using it as an authentication protocol, which was subsequently broken....
ATM cards, as they use the same PIN authentication system and debits are reflected in the user?s account immediately.
The PIN authentication is much more secure than the alternative signature used in offline..
www.tutorgig.com /es/Authentication/9   (734 words)

  
 message authentication code pictures   (Site not responding. Last check: 2007-10-08)
Find information such as authentication mobile phone user, extensible authentication protocol, remote authentication, PHP user authentication, wow authentication key, integrated windows authentication, as Linux authentication, user authentication server, audio tape authentication, user authentication, world of warcraft authentication key and more.
Linux Dictionary: M. MAC (Message Authentication Code) A specific type of message digest where the secret key is included as part of the fingerprint.
The first is authentication: certifying that a message is from whom...
www.user-authentication-server.info-a1.com /userauthenticationserver/10/message-authentication-code-pictures.html   (619 words)

  
 Authentication in TutorGig Encyclopedia   (Site not responding. Last check: 2007-10-08)
Off the record messaging is a technology which provides encryption and authentication for instant messenger conversations by using a public key public private key system.
enable users to be authentication authenticated to each other, and to use the information in public...
MQV Menezes Qu Vanstone is an authentication authenticated protocol cryptography protocol for key agreement....
www.tutorgig.com /es/Authentication/6   (717 words)

  
 HMac (GNU cryptographic primitives and tools, version 2.0.0)
To have a well understood cryptographic analysis of the strength of the authentication mechanism based on reasonable assumptions on the underlying hash function.
To allow for easy replaceability of the underlying hash function in case that faster or more secure hash functions are found or required.
Ensures that the MAC of a pre-determined message is equal to a known pre-computed value.
www.gnu.org /software/gnu-crypto/manual/api/gnu/crypto/mac/HMac.html   (229 words)

  
 Keyed-hash message authentication code   (Site not responding. Last check: 2007-10-08)
Codes, Ciphers and Other Cryptic and Clandestine Communication: 400 Ways to Send Secret Messages from Hieroglyphs to the Internet
Wrixon, Fred B. *Codes, Ciphers and Other Cryptic and Clandestine Communication.* Dimensions: 23.7cm x 21cm x 5.2cm.
It has some very, very simple codes and cyphers explained very easily with simple, amusing illustrations.
www.freeglossary.com /Keyed-Hashing_Message_Authentication   (442 words)

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