Message Authentication Code .

• Message Authentication Code

https://store.theartofservice.com/the-message-authentication-code-toolkit.html

Key (cryptography)

1 In cryptography, a key is a piece of information (a parameter) that determines

the functional output of a cryptographic algorithm or cipher. Without a key, the

algorithm would produce no useful result. In encryption, a key specifies the particular

transformation of plaintext into ciphertext, or vice versa during decryption. Keys are also

used in other cryptographic algorithms, such as digital signature schemes and message

authentication codes.


IPsec Standards Track

1 RFC 4543: The Use of Galois Message Authentication Code (GMAC) in IPsec ESP and

AH


Automated teller machine - Transactional secrecy and integrity

1 Message Authentication Code (MAC) or Partial MAC may also be used to ensure messages have not been tampered with while in transit

between the ATM and the financial network.


Transport Layer Security

1 This allows for data/message confidentiality, and message

authentication codes for message integrity and as a by-product

message authentication


Transport Layer Security - TLS

1 Numbering subsequent Application records with a sequence number and using this sequence number in the

message authentication codes (MACs).


Transport Layer Security - Protocol details

1 Each record can be compressed, padded, appended with a message

authentication code (MAC), or encrypted, all depending on the state

of the connection


Transport Layer Security - TLS record

1 A message authentication code computed over the Protocol

message, with additional key material included. Note that this field

may be encrypted, or not included entirely, depending on the state of

the connection.


Stream cipher attack - Bit-flipping attack

1 Bit-flipping attacks can be prevented by including message authentication code to increase the likelihood that

tampering will be detected.


Cyclic redundancy check - CRCs and data integrity

1 Any application that requires protection against such attacks must

use cryptographic authentication mechanisms, such as message authentication codes or digital

signatures (which are commonly based on cryptographic hash

functions).


ISO 8583 - Data elements

1 64 b 16 Message authentication code

(MAC)


ISO 8583 - Data elements

1 128 b 16 Message authentication code


Encryption - Message verification

1 Encryption, by itself, can protect the confidentiality of messages, but

other techniques are still needed to protect the integrity and authenticity

of a message; for example, verification of a message

authentication code (MAC) or a digital signature


Secure Shell - Version 2.x

1 Better security, for example, comes through Diffie-Hellman key exchange

and strong integrity checking via message authentication codes


SAFER - SAFER+ and SAFER++

1 SAFER+ (Massey et al., 1998) was submitted as a candidate for the

Advanced Encryption Standard and has a block size of 128 bits. The cipher was not

selected as a finalist. Bluetooth uses custom algorithms based on SAFER+ for key derivation (called E21 and E22) and

authentication as message authentication codes (called E1). Encryption in Bluetooth

does not use SAFER+.


Block cipher - Relation to other cryptographic primitives

1 Message authentication codes (MACs) are often built from block

ciphers. CBC-MAC, OMAC and PMAC are such MACs.


Cryptography - Symmetric-key cryptography

1 Message authentication codes (MACs) are much like cryptographic hash functions, except that a secret key can be used to authenticate the

hash value upon receipt.


Application security - Security standards and regulations

1 ISO/IEC 9797-1:1999 Information technology -- Security techniques --

Message Authentication Codes (MACs) -- Part 1: Mechanisms using a

block cipher


Application security - Security standards and regulations

1 ISO/IEC 9797-2:2002 Information technology -- Security techniques --

Message Authentication Codes (MACs) -- Part 2: Mechanisms using a

dedicated hash-function


Internet security - Message Authentication Code

1 A Message Authentication Code is a cryptography method that uses a secret key to encrypt a message. This method outputs a MAC value

that can be decrypted by the receiver, using the same secret key used by the sender. The Message

Authentication Code protects both a message's data integrity as well as

its authenticity.https://store.theartofservice.com/the-message-authentication-code-toolkit.html

Wi-Fi Protected Access - WPA

1 Well tested message authentication codes existed to solve these

problems, but they required too much computation to be used on old

network cards


Wi-Fi Protected Access - Encryption protocol

1 CCMP (Counter Cipher Mode with block chaining message authentication code

Protocol)


Symmetric cryptography - Cryptographic primitives based on symmetric ciphers

1 Encrypting a message does not guarantee that this message is not changed while encrypted. Hence

often a message authentication code is added to a ciphertext to


Symmetric cryptography - Cryptographic primitives based on symmetric ciphers

1 ensure that changes to the ciphertext will be noted by the

receiver. Message authentication codes can be constructed from

symmetric ciphers (e.g. CBC-MAC).


Internet security - Message Authentication Code

1 A Message authentication code|Message Authentication Code is a cryptography

method that uses a Key (cryptography)|secret key to encrypt a message. This

method outputs a MAC value that can be decrypted by the receiver, using the

same secret key used by the sender. The Message Authentication Code protects both a message's data integrity as well

as its Authentication|authenticity.


Authenticated encryption

1 The need for AE emerged from observation that securely

compositing a Block cipher modes of operation|confidentiality mode with an Block cipher modes of operation|authentication mode could be error prone and difficult.people had been doing rather poorly when they tried

to glue together a traditional (privacy-only) encryption scheme

and a message authentication code (MAC), in: it is very easy to

accidentally combine secure encryption schemes with secure

MACs and still get insecure authenticated encryption schemes, in: This was confirmed by a number of practical attacks introduced into

production protocols and applications by incorrect implementation, or lack

of, authentication (including Transport Layer Security|SSL/TLS).



1 ** Output: ciphertext and authentication tag (Message

Authentication Code)



1 However, authenticated encryption can be generically constructed by

combining an encryption scheme and a Message Authentication Code

(MAC), provided that the encryption scheme is semantic security|

semantically secure under chosen plaintext attack and the MAC

function is unforgeable under chosen message attack


Cryptographic hash function

1 Cryptographic hash functions have many information security

applications, notably in digital signatures, message authentication codes (MACs), and other forms of

authentication


Cryptographic hash function - Use in building other cryptographic primitives

1 Message authentication codes (MACs) (also called keyed hash

functions) are often built from hash functions. HMAC is such a MAC.


IEEE 802.1AE

1 ** Message authentication code

(ICV)


Secure Sockets Layer


authentication codes for message integrity and as a by-product,



Secure Sockets Layer - TLS

1 * Numbering subsequent Application records with a sequence number and using this sequence number in the

message authentication codes (MACs).


Secure Sockets Layer - Protocol details

1 Each record can be compressed, padded, appended with a message

authentication code (MAC), or encrypted, all depending on the state

of the connection


Secure Sockets Layer - TLS record

1 : A message authentication code computed over the Protocol

message, with additional key material included. Note that this field

may be encrypted, or not included entirely, depending on the state of

the connection.


Cipher suite

1 A 'cipher suite' is a named combination of authentication,

encryption, and message authentication code (MAC)

algorithms used to negotiate the security settings for a network

connection using the Transport Layer Security (TLS) / Secure Sockets Layer

(SSL) network protocol.


Cipher suite - Detailed description

1 Each named cipher suite defines a key exchange algorithm, a bulk

encryption algorithm, a message authentication code (MAC) algorithm, and a pseudorandom function (PRF).

(RFC 5246, p. 40)


Cipher suite - Detailed description

1 * The 'message authentication code' (MAC) algorithm is used to create the

message digest, a cryptographic hash of each Block

(telecommunications)|block of the message stream. (RFC 5246, p. 17)


Cipher suite - Examples of algorithms used

1 ;message authentication: for TLS, a HMAC|Hash-based Message

Authentication Code using MD5 or one of the Secure Hash Algorithm

(disambiguation)|SHA hash functions is used. For SSL, Secure Hash

Algorithm (disambiguation)|SHA, MD5, MD4, and MD2 (cryptography)|

MD2 are used.


Galois/Counter Mode

1 It is an authenticated encryption algorithm designed to provide both

data authenticity (integrity) and confidentiality. GCM is defined for

block ciphers with a block size of 128 bits. 'Galois Message Authentication Code' ('GMAC') is an authentication-

only variant of the GCM which can be used as an incremental message

authentication code. Both GCM and GMAC can accept initialization

vectors of arbitrary length.


Galois/Counter Mode - Use

1 GCM mode is used in the IEEE 802.1AE (MACsec) Ethernet security, 802.11ad|IEEE 802.11ad (also known as WiGig), ANSI (INCITS) Fibre Channel Security Protocols (FC-SP), IEEE P1619.1 tape storage, Internet Engineering Task

Force|IETF IPsec standards,RFC 4106 The Use of Galois/Counter Mode (GCM) in IPsec Encapsulating Security Payload (ESP)RFC 4543 The Use of Galois

Message Authentication Code (GMAC) in IPsec ESP and AH Secure Shell|SSH RFC 5647 AES Galois Counter Mode for the Secure Shell Transport Layer Protocol and Transport

Layer Security|TLS 1.2.RFC 5288 AES Galois Counter Mode (GCM) Cipher Suites for TLSRFC 6367 Addition of the

Camellia Cipher Suites to Transport Layer Security (TLS) AES-GCM is included into the NSA Suite B Cryptography.


Galois/Counter Mode - Security

1 The authentication strength depends on the length of the authentication tag, as with all symmetric message

authentication codes


Galois/Counter Mode - Security

1 As with any message authentication code, if the adversary chooses a t-bit tag at

random, it is expected to be correct for given data with probability 2−t. With GCM,

however, an adversary can choose tags that increase this probability, proportional to the total length of the ciphertext and additional

authenticated data (AAD). Consequently, GCM is not well-suited for use with very

short tag lengths or very long messages.


Internet Protocol Security - Standards Track

1 * RFC 4543: The Use of Galois Message Authentication Code (GMAC) in IPsec ESP and

AH


ARC4 - Security

1 If not used together with a strong message authentication code (MAC), then encryption is vulnerable to a bit-

flipping attack


Outline of cryptography - Cryptographic hash functions

1 * Keyed-hash message

authentication code -


WS-Security - Issues

1 * If only Padding (cryptography)|CBC mode encryption/decryption is

applied or if the CBC mode decryption is applied without

verifying a secure checksum (Digital Signature|signature or Message authentication code|MAC) before

decryption then the implementation is likely to be vulnerable to padding

oracle attacks.https://store.theartofservice.com/the-message-authentication-code-toolkit.html

Error correction - Cryptographic hash functions

1 If an attacker can change not only the message but also the hash value,

then a keyed hash or message authentication code (MAC) can be

used for additional security


Message authentication code

1 In cryptography, a 'message authentication code' (often 'MAC') is a short piece of information used to

Authentication|authenticate a message and to provide integrity and

authenticity assurances on the message. Integrity assurances detect accidental and intentional message

changes, while authenticity assurances affirm the message's

origin. https://store.theartofservice.com/the-message-authentication-code-toolkit.html

Message authentication code - Standards

1 * ISO/IEC 9797-1 Mechanisms using a block cipher[

http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=30656 ISO/IEC 9797-1 Information technology — Security

techniques — Message Authentication Codes (MACs) — Part 1: Mechanisms using a block cipher]


Message authentication code - Standards

1 * ISO/IEC 9797-2 Mechanisms using a dedicated hash-function[

http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=31136 ISO/IEC 9797-2 Information technology — Security

techniques — Message Authentication Codes (MACs) — Part

2: Mechanisms using a dedicated hash-function]


Message authentication code - One-time MAC

1 Universal hashing and in particular pairwise independent hash functions

provide a message authentication code as long as the key is used at

most once (or less than k-times for k-wise independent hash functions.

This can be seen as of the one-time pad for authentication.


Chip Authentication Program - Protocol details

1 This confirmation message contains a message authentication code

(typically CBC-MAC/Triple DES) that is generated with the help of a card-

specific secret key stored securely in the smartcard


NIST SP 800-90A

1 The publication contains the specification for four

cryptographically secure pseudorandom number generators for use in cryptography: Hash DRBG

(based on hash functions), HMAC DRBG (Based on Hash-based

message authentication code), CTR DRBG (based on block ciphers), and

Dual_EC_DRBG (based on elliptic curve cryptography)


Block ciphers - Relation to other cryptographic primitives

1 * Message authentication codes (MACs) are often built from block ciphers. CBC-MAC, One-key MAC|OMAC and PMAC (cryptography)|

PMAC are such MACs.


One-way function - Theoretical implications of one-way functions

1 *Message authentication

codes


Cryptography standards - U.S. Government Federal Information Processing Standards (FIPS)

1 *FIPS PUB 198 The Keyed-Hash

Message Authentication Code

(HMAC) 2002https://store.theartofservice.com/the-message-authentication-code-toolkit.html

Threema - Security

1 A 128 bit message authentication code is added to the message to

detect manipulations, as well as a random amount of cryptographic padding to prevent inferences or

changes being made to the content of the message.


Block cipher modes of operation - History and standardization

1 HMAC was approved in 2002 as [http://csrc.nist.gov/publications/fips/fips198/fips-

198a.pdf FIPS 198], The Keyed-Hash Message Authentication Code (HMAC), CMAC was released in

2005 under [http://csrc.nist.gov/publications/nistpubs/800-38B/SP_800-38B.pdf SP800-38B], Recommendation for Block

Cipher Modes of Operation: The CMAC Mode for Authentication, and GMAC was formalized in 2007

under [http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf SP800-38D], Recommendation for Block Cipher Modes of Operation: Galois/Counter

Mode (GCM) and GMAC.


Digest access authentication - Impact of MD5 security on digest authentication

1 The HTTP scheme was designed by Phillip Hallam-Baker at CERN in 1993 and does not incorporate subsequent

improvements in authentication systems, such as the development of keyed-hash message authentication

code (HMAC)


List of International Organization for Standardization standards - ISO 5000 – ISO 9999

1 * ISO/IEC 9797 Information technology – Security techniques – Message Authentication

Codes (MACs)


Sender Rewriting Scheme - The Rewriting Scheme

1 * 'The' Hash-based message authentication code (HHH) is

computed against a local secret, but only a part of it is used; for example,

storing the first 4 characters of a base64 representation provides 24

bits of security. The hash is checked by the domain who generated it, in

case a bounce arrives.


SMTP Authentication - History

1 John Gardiner Myers published the first draft of SMTP AUTH in 1995, and it has been

successively developed and discussed in the IETF along with mail submission protocol,

Extended SMTP (ESMTP), and Simple Authentication and Security Layer (SASL). An

older SASL mechanism for ESMTP authentication (ESMTPA) is CRAM-MD5, and uses of the MD5 algorithm in HMACs (hash-based message authentication codes) are

still considered sound.


Jungle Disk - Criticism

1 * The lack of a Message Authentication Code means that file corruption (accidental or

deliberate) or arbitrary file content insertionsIf the people running the underlying

storage service (Amazon S3 or Rackspace Cloud Files) know the contents of a file stored via Jungle Disk, they could transform it into

anything they want — planting files which are dangerous (e.g., viruses) or even illegal (e.g., child pornography). Percival 2011 will not be

detected


AES-CCMP

1 'Counter Mode Cipher Block Chaining Message Authentication Code

Protocol', 'Counter Mode CBC-MAC Protocol' or simply 'CCMP' ('CCM mode Protocol') is an encryption

security protocol|protocol designed for Wireless LAN products that

implement the standards of the IEEE 802.11i amendment to the original

IEEE 802.11 standardhttps://store.theartofservice.com/the-message-authentication-code-toolkit.html

AES-CCMP - Technical details

1 Lastly are the Message authentication code|Message

Integrity Code (MIC) which protects the integrity and authenticity of the

packet and the frame check sequence (FCS) which is used for

error detection and correction


HTTPsec - Example with explanation

1 The responder is authenticated in the initialization stage, by the validating the

signature against the public key presented by its certificate (authentication freshness is

ensured by the requester's nonce). The requester is subsequently authenticated in the continuation stage by the use of HMAC

message authentication codes (authentication freshness is ensured by the

requester's ability to decrypt the responders's nonce).


HTTPsec - Example with explanation

1 * The secret keys are inputs to message authentication codes and message body

encryption. As the keys are only known by the two legitimate peers, they are used

by the message-receiving peer to validate the message-sending peer, and to

decrypt the message body. Additionally, message uniqueness is enforced by an incrementing counter, which is one of various inputs to the message's MAC.


Encryption key

1 In cryptography, a 'key' is a piece of information (a parameter) that determines

the functional output of a cryptographic algorithm or cipher. Without a key, the

algorithm would produce no useful result. In encryption, a key specifies the particular

transformation of plaintext into ciphertext, or vice versa during decryption. Keys are also

used in other cryptographic algorithms, such as digital signature schemes and message

authentication codes.


Bilateral key exchange

1 A Bilateral Key allowed secure communication across the SWIFT|SWIFT Network. The text of a SWIFT:Message Types and the authentication

key were used to generate a Message Authentication Code or MAC. The MAC ensured the origin of a message and the authenticity of

the message contents. This was normally accomplished by the exchange of various FIN Message|SWIFT Messages used specifically for

establishing a communicating key pair.


Cryptographic Message Syntax

1 The 'Cryptographic Message Syntax' (CMS) is the IETF's standard for Cryptography|cryptographically protected messages. It can be used

to Digital signature|digitally sign, Cryptographic hash function|digest,

Message authentication code|authenticate or encryption|encrypt

any form of digital data.


SSL encryption


authentication codes for message integrity and as a by-product,



SSL encryption - Data integrity

1 Message authentication code (MAC) is used for data integrity. HMAC is

used for Cipher block chaining|CBC mode of block ciphers and stream

ciphers. AEAD block cipher modes of operation|AEAD is used for

Authenticated encryption such as Galois/Counter Mode|GCM mode and

CCM mode.


List of algorithms - Cryptography

1 ** keyed-hash message authentication code|HMAC: keyed-hash message authentication


Encrypt - Message verification

1 Encryption, by itself, can protect the confidentiality of messages, but

other techniques are still needed to protect the integrity and authenticity

of a message; for example, verification of a message

authentication code (MAC) or a digital signature


Project 25 - Jamming vulnerability

1 As a result bit errors may be expected in typical transmissions,

and while harmless for voice communication, the presence of such

errors force the use of stream ciphers, which can tolerate bit errors, and prevents the use of a standard technique, message authentication codes (MACs), to protect message

integrity from stream cipher attackshttps://store.theartofservice.com/the-message-authentication-code-toolkit.html

Selective forgery

1 In a cryptography|cryptographic digital signature or Message

Authentication Code|MAC system, 'digital signature forgery' is the

ability to create a pair consisting of a message m and a signature (or MAC) \sigma that is valid for m,

where m has not been signed in the past by the legitimate signer. There

are three types of forgery: existential, selective, and universal.


Integrated Encryption Scheme

1 ** Message authentication code|MAC, e.g., HMAC-SHA-1-160 with 160-bit keys or HMAC-SHA-1-80 with 80-bit

keys;


VMAC

1 'VMAC' is a block cipher-based message authentication code (MAC)

algorithm using a universal hash proposed by Ted Krovetz and Wei Dai

in April 2007. The algorithm was designed for high performance backed by a formal analysis.


VMAC - Specification

1 See internet draft [http://fastcrypto.org/vmac/draft-

krovetz-vmac-01.txt VMAC: Message Authentication Code using Universal

Hashing]


Malleability (cryptography) - Example malleable cryptosystems

1 For this and many other reasons, using Message authentication code|

message authentication codes is needed to guard against this method

of tampering.


CRYPTREC - e-Government Recommended Ciphers List

1 **Hash-based message

authentication code|HMAC: NIST FIPS

PUB 198-1https://store.theartofservice.com/the-message-authentication-code-toolkit.html

Automatic teller machine - Transactional secrecy and integrity

1 Message Authentication Code (MAC) or Partial MAC may also be used to ensure messages have not been tampered with while in transit

between the ATM and the financial network.


Message Integrity Code - Standards

1 * ISO/IEC 9797-1 Mechanisms using a block

cipher[http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=30656 ISO/IEC 9797-1 Information technology — Security

techniques — Message Authentication Codes (MACs) — Part 1: Mechanisms using a block cipher]


Message Integrity Code - Standards

1 * ISO/IEC 9797-2 Mechanisms using a dedicated

hash-function[http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue

_detail.htm?csnumber=31136 ISO/IEC 9797-2 Information

technology — Security techniques — Message Authentication Codes

(MACs) — Part 2: Mechanisms using a dedicated hash-function]


ISO/IEC 9797-1

1 'ISO/IEC 9797-1' Information technology – Security techniques – Message Authentication Codes (MACs) – Part 1: Mechanisms using a block

cipher[http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=30656 ISO/IEC 9797-1:1999 Information technology – Security techniques – Message Authentication

Codes (MACs) – Part 1: Mechanisms using a block cipher] is an international standard that defines

methods for calculating a message authentication code (MAC) over data.


Station-to-Station protocol - STS-MAC

1 In cases where encryption is a not viable choice in session

establishment, K can instead be used to create a message authentication

code|MAC.


PMAC (cryptography)

1 'PMAC', which stands for 'Parallelizable MAC', is a message authentication code algorithm. It was created by Phillip Rogaway

(patent pending).


PMAC (cryptography)

1 PMAC is a method of taking a block cipher and creating an efficient

message authentication code that is provably reducible in security to the

underlying block cipher.


SipHash - Overview

1 SipHash computes 64-bit message authentication code from a variable-length message and 128-bit secret key. It was designed to be efficient

even for short inputs, with performance comparable to non-

cryptographic hash functions, such as CityHash,


OMAC (cryptography)

1 'OMAC (One-key MAC)' is a message authentication code

constructed from a block cipher much like the CBC-MAC algorithm.


Replay attack - Countermeasures

1 Bob can also send Cryptographic nonce|nonces but should then

include a message authentication code (MAC), which Alice should

check.


List of cryptographic key types

1 * 'authentication key' - Key used in a keyed-hash message authentication code, or HMAC.


CipherSuite

1 A 'cipher suite' is a named combination of authentication,

encryption, message authentication code (MAC) and Key_exchange | key

exchange algorithms used to negotiate the security settings for a

network connection using the Transport Layer Security (TLS) /

Secure Sockets Layer (SSL) network protocol.


SILC (protocol) - Components

1 The packets are secured using algorithms based on symmetric

cryptography and authenticated by using Message Authentication Code

algorithm, HMAC.


Data Authentication Algorithm

1 The 'Data Authentication Algorithm' ('DAA') is a former Federal Information Processing Standard|U.S. government standard for producing

cryptographic message authentication codes. According to

the standard, a code produced by the DAA is called a 'Data Authentication Code' ('DAC'). The algorithm is not

considered secure by today's standards.


Length extension attack

1 In cryptography and computer security, 'length extension attacks' are a type of Attack (computing)|attack when certain types of Hash

function|hashes are misused as message authentication codes, allowing for inclusion of extra

information.


Length extension attack - Example

1 The server would perform the request given (to deliver a waffle of type eggo to the given location for user 1) only if the signature is valid

for the user. The signature used here is a Message authentication code|

MAC, signed with a key not known to the attacker. (This example is also vulnerable to a replay attack, by sending the same request and

signature a second time.)https://store.theartofservice.com/the-message-authentication-code-toolkit.html

OCB mode - Encryption and authentication

1 OCB mode was designed to provide both authentication and privacy. It is essentially a

scheme for integrating a Message Authentication Code (MAC) into the

operation of a block cipher. In this way, OCB mode avoids the need to use two systems: a MAC for authentication and

encryption for privacy. This results in lower computational cost compared to using separate encryption and authentication

functions.https://store.theartofservice.com/the-message-authentication-code-toolkit.html

TCP Fast Open - Details

1 The cookie is generated by applying a block cipher keyed on a key held

secret by the server to the client's IP address, generating a Message

authentication code|MAC tag that cannot be forged.


MMH-Badger MAC

1 In cryptography, to guarantee the integrity of a message, one can use

either public key digital signatures or use a Message Authentication Code

(MAC)


MMH-Badger MAC - Introduction

1 Carter and Wegman introduced universal hashing to construct a message

authentication codes (MACs)


MMH-Badger MAC - Universal hash function families

1 Universal hashing was first introduced by Carter and Wegman in 1979 and was studied further by Sarwate, Wegman and Carter and

Stinson. Universal hashing has many important applications in theoretical

computer science and was used by Wegman and Carter in the construction of message authentication codes (MACs) in. Universal

hashing can be defined as a mapping from a finite set A with size a to a finite set B with

size b.


Poly1305-AES

1 'Poly1305-AES' is a Cryptography|cryptographic message

authentication code (MAC) written by Daniel J. Bernstein. It can be used to

verify the data integrity and the authenticity of a message.


Cryptographic key types

1 An example with devastating consequences is the reuse of the same symmetric key algorithm|

symmetric key for both symmetric message authentication code|authentication in CBC-MAC and

symmetric data encryption in block cipher modes of operation|CBC

encryption.


Cryptographic key types

1 ; Private key transport key: Private key transport keys are the private keys of asymmetric key pairs that are used to

decrypt keys that have been encrypted with the associated public key using a public key

algorithm. Key transport keys are usually used to establish keys (e.g., key wrapping

keys, data encryption keys or message authentication code|MAC keys) and,

optionally, other keying material (e.g., initialization vectors).


CMAC

1 In cryptography, 'CMAC' (Cipher-based MAC) is a block cipher-based

message authentication code algorithm. It may be used to provide assurance of the authenticity and, hence, the integrity of binary data.

This block cipher modes of operation|mode of operation fixes security

deficiencies of CBC-MAC (CBC-MAC is secure only for fixed-length

messages).https://store.theartofservice.com/the-message-authentication-code-toolkit.html

Padding oracle attack - Solution

1 To prevent this attack, one could append an HMAC (Hash-based

message authentication code) to the ciphertext. Without the key used to

generate the HMAC, an attacker won't be able to produce valid ciphertexts. Since the HMAC is

checked before the decryption stage, the attacker cannot do the required

bit-fiddling and hence cannot discover the plaintext.


Initialization vector

1 Randomization is also required for other primitives, such as universal

hash functions and message authentication codes based thereon.


CBC-MAC

1 In cryptography, a 'cipher block chaining message authentication

code' ('CBC-MAC') is a technique for constructing a message

authentication code from a block cipher


CBC-MAC - Security with fixed and variable-length messages

1 [http://www.cs.ucdavis.edu/research/tech-reports/1997/CSE-97-

15.pdf The security of the cipher block chaining message

authentication code.] JCSS 61(3):362–399, 2000


CBC-MAC - Using the same key for encryption and authentication

1 By definition, a Message Authentication Code is broken if we

can find a different message (a sequence of plain-text pairs P') which

produces the same tag as the previous message, P, with P \not = P'


CBC-MAC - Using the same key for encryption and authentication

1 However, due to the MAC's usage of a different key K_2, we cannot undo

the decryption process in the forward step of the computation of the

message authentication code so as to produce the same tag; each

modified P_i' will now be encrypted by K_2 in the CBC-MAC process to

some value MAC_i \not = C_i'.


CBC-MAC - Allowing the initialisation vector to vary in value

1 When computing a message authentication code, such as by CBC-

MAC, the use of an initialisation vector is a possible attack vector.


Lucky Thirteen attack - Attack

1 It is a novel variant of Serge Vaudenay's padding oracle attack

that had previously thought to have been fixed, that uses a timing side-channel attack against the message

authentication code (MAC) check stage in the TLS algorithm to break the algorithm in a way that was not

fixed by previous attempts to mitigate Vaudenay's attack.


Trusted timestamping - Classification

1 * Message authentication code|MAC - simple secret key based scheme,

found in ANSI ASC X9.95 Standard.


UMAC

1 In cryptography, a 'message authentication code based on

universal hashing', or 'UMAC', is a type of message authentication code

(MAC) calculated choosing a hash function from a class of hash

functions according to some secret (random) process and applying it to

the message


LibreSSL - Cryptographic

1 In terms of notable additions made, OpenBSD has added support for

newer and more reputable algorithms (ChaCha (cipher)|ChaCha stream cipher and Poly1305 message

authentication code) along with a safer set of elliptic curve

cryptography|elliptic curves (brainpool curves from

RFC5639,http://tools.ietf.org/html/rfc5639 up to 512 bits in strength).


Mac & Devin Go to High School (soundtrack) - Technology

1 * Message authentication code, used to authenticate a message in cryptography


Windows Media DRM - How it works

1 An analysis of version 2 of the DRM scheme in Windows Media Audio

revealed that it was using a combination of elliptic curve

cryptography key exchange, the Data Encryption Standard|DES block cipher, a custom block cipher dubbed

MultiSwap (for message authentication code|MACs only), the RC4 cipher|RC4 stream cipher, and

the SHA-1 hashing function.https://store.theartofservice.com/the-message-authentication-code-toolkit.html

Deniable encryption - Deniable authentication

1 This is achieved by the fact that all information necessary to forge messages is appended to the

encrypted messages ndash; if an adversary is able to create digitally

authentic messages in a conversation (see hash-based message authentication code

(HMAC)), he is also able to forgery|forge messages in the conversation


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Message Authentication Code .

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