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Code::Blocks is an open source Integrated Development Environment (IDE). This will aid you compiling and debugging C and C programs. This page will help you download the Code::Blocks IDE installation file (which includes the complier and debugger). Instruction Guide: There is also a guide to help you setup and use Code::Blocks. If you have code that you’d like to reuse, Codesters allows you to store it inside a custom block. To create your own custom block, follow these directions: Step 1: Highlight the code in your editor you’d like to reuse and press CTRL - C (Windows) or CMD - C (Mac) to copy the text. Connect and share knowledge within a single location that is structured and easy to search. One-key MAC (OMAC) is a message authentication code constructed from a block cipher much like the CBC-MAC algorithm. Officially there are two OMAC algorithms (OMAC1 and OMAC2) which are both essentially the same except for a small tweak. OMAC1 is equivalent to CMAC, which became an NIST recommendation in May 2005. Code::Blocks The free C/C and Fortran IDE. Code::Blocks is a free C/C and Fortran IDE built to meet the most demanding needs of its users. It is designed to be very extensible and fully configurable. Built around a plugin framework, Code::Blocks can be extended with plugins. Any kind of functionality can be added by installing/coding a plugin.

One-key MAC (OMAC) is a message authentication code constructed from a block cipher much like the CBC-MAC algorithm.

Officially there are two OMAC algorithms (OMAC1 and OMAC2) which are both essentially the same except for a small tweak. OMAC1 is equivalent to CMAC, which became an NIST recommendation in May 2005.

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It is free for all uses: it is not covered by any patents.^[1]In cryptography, CMAC (Cipher-based Message Authentication Code)^[2] 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 mode of operation fixes security deficiencies of CBC-MAC (CBC-MAC is secure only for fixed-length messages).

The core of the CMAC algorithm is a variation of CBC-MAC that Black and Rogaway proposed and analyzed under the name XCBC^[3] and submitted to NIST.^[4] The XCBC algorithm efficiently addresses the security deficiencies of CBC-MAC, but requires three keys. Iwata and Kurosawa proposed an improvement of XCBC and named the resulting algorithm One-Key CBC-MAC (OMAC) in their papers.^[5] They later submitted OMAC1,^[6] a refinement of OMAC, and additional security analysis.^[7] The OMAC algorithm reduces the amount of key material required for XCBC. CMAC is equivalent to OMAC1.

To generate an ℓ-bit CMAC tag (t) of a message (m) using a b-bit block cipher (E) and a secret key (k), one first generates two b-bit sub-keys (k₁ and k₂) using the following algorithm (this is equivalent to multiplication by x and x² in a finite field GF(2^b)). Let ≪ denote the standard left-shift operator and ⊕ denote bit-wise exclusive or:

1. Calculate a temporary value k₀ = E_k(0).
2. If msb(k₀) = 0, then k₁ = k₀ ≪ 1, else k₁ = (k₀ ≪ 1) ⊕ C; where C is a certain constant that depends only on b. (Specifically, C is the non-leading coefficients of the lexicographically first irreducible degree-b binary polynomial with the minimal number of ones: 0x1B for 64-bit, 0x87 for 128-bit, and 0x425 for 256-bit blocks.)
3. If msb(k₁) = 0, then k₂ = k₁ ≪ 1, else k₂ = (k₁ ≪ 1) ⊕ C.
4. Return keys (k₁, k₂) for the MAC generation process.

As a small example, suppose b = 4, C = 0011₂, and k₀ = E_k(0) = 0101₂. Then k₁ = 1010₂ and k₂ = 0100 ⊕ 0011 = 0111₂.

The CMAC tag generation process is as follows:

1. Divide message into b-bit blocks m = m₁ ∥ ... ∥ m_n−1 ∥ m_n, where m₁, ..., m_n−1 are complete blocks. (The empty message is treated as one incomplete block.)
2. If m_n is a complete block then m_n′ = k₁ ⊕ m_n else m_n′ = k₂ ⊕ (m_n ∥ 10...0₂).
3. Let c₀ = 00...0₂.
4. For i = 1, ..., n − 1, calculate c_i = E_k(c_i−1 ⊕ m_i).
5. c_n = E_k(c_n−1 ⊕ m_n′)
6. Output t = msb_ℓ(c_n).

The verification process is as follows:

1. Use the above algorithm to generate the tag.
2. Check that the generated tag is equal to the received tag.

Implementations[edit]

• Python implementation: see the usage of the AES_CMAC() function in 'impacket/blob/master/tests/misc/test_crypto.py', and its definition in 'impacket/blob/master/impacket/crypto.py'.^[8]
• Ruby implementation ^[9]

References[edit]

1. ^Rogaway, Phillip. 'CMAC: Non-licensing'. Retrieved May 27, 2020. Phillip Rogaway's statement on intellectual property status of CMAC
2. ^Dworkin, M J (2016). 'Recommendation for block cipher modes of operation'(PDF). doi:10.6028/nist.sp.800-38b.Cite journal requires |journal= (help)
3. ^Black, John; Rogaway, Phillip (2000-08-20). Advances in Cryptology – CRYPTO 2000. Springer, Berlin, Heidelberg. pp. 197–215. doi:10.1007/3-540-44598-6_12. ISBN978-3540445982.
4. ^Black, J; Rogaway, P. 'A Suggestion for Handling Arbitrary-Length Messages with the CBC MAC'(PDF).Cite journal requires |journal= (help)
5. ^Iwata, Tetsu; Kurosawa, Kaoru (2003-02-24). 'OMAC: One-Key CBC MAC'. Fast Software Encryption. Lecture Notes in Computer Science. 2887. Springer, Berlin, Heidelberg. pp. 129–153. doi:10.1007/978-3-540-39887-5_11. ISBN978-3-540-20449-7.
6. ^Iwata, Tetsu; Kurosawa, Kaoru (2003). 'OMAC: One-Key CBC MAC – Addendum'(PDF).Cite journal requires |journal= (help)
7. ^Iwata, Tetsu; Kurosawa, Kaoru (2003-12-08). 'Stronger Security Bounds for OMAC, TMAC, and XCBC'. In Johansson, Thomas; Maitra, Subhamoy (eds.). Progress in Cryptology – INDOCRYPT 2003. Lecture Notes in Computer Science. Springer Berlin Heidelberg. pp. 402–415. CiteSeerX10.1.1.13.8229. doi:10.1007/978-3-540-24582-7_30. ISBN9783540206095.
8. ^'Impacket is a collection of Python classes for working with network protocols.: SecureAuthCorp/impacket'. 15 December 2018 – via GitHub.
9. ^'Ruby C extension for the AES-CMAC keyed hash function (RFC 4493): louismullie/cmac-rb'. 4 May 2016 – via GitHub.

External links[edit]

• RFC 4493 The AES-CMAC Algorithm
• RFC 4494 The AES-CMAC-96 Algorithm and Its Use with IPsec
• RFC 4615 The Advanced Encryption Standard-Cipher-based Message Authentication Code-Pseudo-Random Function-128 (AES-CMAC-PRF-128)
• OMAC Online Test

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Digest::CMAC - The One-key CBC MAC message authentication code.

This module implements OMAC1 blockcipher-based message authentication code for perl. For OMAC1/OMAC. Check http://www.nuee.nagoya-u.ac.jp/labs/tiwata/omac/omac.html. Here is an excerpt of that page

OMAC is a blockcipher-based message authentication code designed and analyzed by me and Kaoru Kurosawa.

OMAC is a simple variant of the CBC MAC (Cipher Block Chaining Message Authentication Code). OMAC stands for One-Key CBC MAC.

OMAC allows and is secure for messages of any bit length (while the CBC MAC is only secure on messages of one fixed length, and the length must be a multiple of the block length). Also, the efficiency of OMAC is highly optimized. It is almost as efficient as the CBC MAC.

'NIST Special Publication 800-38B Recommendation for Block Cipher Modes of Operation: the CMAC Mode for Authentication' has been finalized on May 18, 2005. This Recommendation specifies CMAC, which is equivalent to OMAC (OMAC1).

Like many block-cipher's Crypt:: modules like Crypt::Rijndael, and MIME::Base64.

This creates a new Digest::CMAC object, using $key.

$cipher is 'Crypt::Rijndael'(default), 'Crypt::Misty1', Crypt::Blowfish', or whatever blockcipher you like. $key is fixed length string that blockcipher demands.

The $message provided as argument are appended to the message we calculate the MAC. The return value is the $cmac object itself;

This is just an alias for $cmac->new;

Return the binary authentication code for the message. The returned string will be blockcipher's block size.

Same as $cmac->digest, but will return the digest in hexadecimal form.

Same as $omac1->digest, but will return the digest as a base64 encoded string.

Crypt::Rijndael, http://www.nuee.nagoya-u.ac.jp/labs/tiwata/omac/omac.html, http://www.csrc.nist.gov/publications/nistpubs/800-38B/SP_800-38B.pdf

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OMAC designed and analyzed by Tetsu Iwata and Kaoru Kurosawa

'Crypt::CMAC' was written by Hiroyuki OYAMA <oyama@module.jp>

OMAC2 support added by Yuval Kogman

Copyright (C) 2006 by Hiroyuki OYAMA, 2007 by Hiroyuki OYAMA, Yuval Kogman

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.6 or, at your option, any later version of Perl 5 you may have available.

1 POD Error

The following errors were encountered while parsing the POD:

=back doesn't take any parameters, but you said =back 4

To install Digest::CMAC, copy and paste the appropriate command in to your terminal.

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For more information on module installation, please visit the detailed CPAN module installation guide.