This website does readability filtering of other pages. All styles, scripts, forms and ads are stripped. If you want your website excluded or have other feedback, use this form.

SearchSecurity
Definition

# Rijndael

WhatIs.com Follow: Contributor(s): Borys Pawliw

Rijndael (pronounced rain-dahl) is the algorithm that has been selected by the U.S. National Institute of Standards and Technology (NIST) as the candidate for the Advanced Encryption Standard (AES). It was selected from a list of five finalists, that were themselves selected from an original list of more than 15 submissions. Rijndael will begin to supplant the Data Encryption Standard (DES) - and later Triple DES - over the next few years in many cryptography applications. The algorithm was designed by two Belgian cryptologists, Vincent Rijmen and Joan Daemen, whose surnames are reflected in the cipher's name. Rijndael has its origins in Square, an earlier collaboration between the two cryptologists.

The Rijndael algorithm is a new generation symmetric block cipher that supports key sizes of 128, 192 and 256 bits, with data handled in 128-bit blocks - however, in excess of AES design criteria, the block sizes can mirror those of the keys. Rijndael uses a variable number of rounds, depending on key/block sizes, as follows:

9 rounds if the key/block size is 128 bits

11 rounds if the key/block size is 192 bits

13 rounds if the key/block size is 256 bits

Rijndael is a substitution linear transformation cipher, not requiring a Feistel network. It use triple discreet invertible uniform transformations (layers). Specifically, these are: Linear Mix Transform; Non-linear Transform and Key Addition Transform. Even before the first round, a simple key addition layer is performed, which adds to security. Thereafter, there are Nr-1 rounds and then the final round. The transformations form a State when started but before completion of the entire process.

The State can be thought of as an array, structured with 4 rows and the column number being the block length divided by bit length (for example, divided by 32). The cipher key similarly is an array with 4 rows, but the key length divided by 32 to give the number of columns. The blocks can be interpreted as unidimensional arrays of 4-byte vectors.

The exact transformations occur as follows: the byte subtransformation is nonlinear and operates on each of the State bytes independently - the invertible S-box (substitution table) is made up of 2 transformations. The shiftrow transformation sees the State shifted over variable offsets. The shift offset values are dependent on the block length of the State. The mixcolumn transformation sees the State columns take on polynomial characteristics over a Galois Field values (28), multiplied x4 + 1 (modulo) with a fixed polynomial. Finally, the roundkey transform is XORed to the State. The key schedule helps the cipher key determine the round keys through key expansion and round selection.

Overall, the structure of Rijndael displays a high degree of modular design, which should make modification to counter any attack developed in the future much simpler than with past algorithm designs.

#### Was the best choice really Rijndael?

Our Cryptography expert, Borys Pawliw comments: "The AES selection was always going to be a compromise, balancing various factors such as overall security, performance, and efficiency. As such, it was unlikely that the selection of any one algorithm would receive unanimous praise from all quarters. Rijndael's selection has been criticized by some because the algorithm does not appear to be as secure as some of the other choices.

This criticism is valid theoretically, but does not mean that data secured using this algorithm is going to be unacceptably vulnerable to attack. Although Rijndael may not have been the most secure algorithm from an academic viewpoint, defenders claim that it is more than likely secure enough for all applications in the real world and can be enhanced by simply adding more rounds. Attacks on the algorithm have succeeded only in an extremely limited environment and, while interesting from a mathematical viewpoint, appear to have little consequence in the real world."

This was last updated in May 2007

#### Related Terms

The Advanced Encryption Standard, or AES, is a symmetric block cipher used by the U.S. government to protect classified ... See complete definition
cryptanalysis
Cryptanalysis is the study of ciphertext, ciphers and cryptosystems with the aim of understanding how they work and finding and ... See complete definition
email spam
Email spam, or junk email, is unsolicited bulk messages sent through email with commercial, fraudulent or malicious intent. See complete definition

## SearchCloudSecurity

• ### How to monitor AWS credentials with the new Trailblazer tool

A security researcher introduced a tool called Trailblazer, which aims to simplify monitoring AWS credentials. Expert Dave ...

• ### The time to consider SIEM as a service has arrived

Now even your SIEM comes in the as-a-service model. Assess whether it's time to consider outsourcing this fundamental tool in ...

• ### How the NetSpectre vulnerability affects the cloud

The NetSpectre vulnerability performs side-channel attacks to read data across networks. Learn how to use threat modeling to stop...

## SearchNetworking

• ### VMware faces strong challengers in cloud systems management

VMware topped IDC's latest vendor ranking in the cloud systems management market. But the analyst firm said the market is too ...

• ### How SD-WAN services could improve application metrics

In this roundup of network blogs, industry insiders dissect SD-WAN's role in application metrics, the future of 5G growth and the...

• ### Comcast gigabit service ready in 39 states

Comcast gigabit cable is now available to 58 million homes and businesses in 39 states. Comcast completed the rollout as AT&T and...

## SearchCIO

• ### How secure-by-design ITSM processes can be a business differentiator

Secure ITSM procedures are essential to digital organizations' data protection processes. They can also be a bottom line boon, ...

• ### Staring down cybersecurity risks in the digital organization

For cybersecurity strategies to be successful, digitized companies must find the balance between the benefits and risks that come...

• ### Embedded IT, global talent to define future of IT jobs

As more businesses identify as tech companies, what's the future of IT jobs? Many IT teams will work remotely on a gig-by-gig ...

## SearchEnterpriseDesktop

• ### How to manage cookie privacy in the enterprise

Cookies can make life easier for users by preventing them from having to re-enter passwords and preferences on websites, but they...

• ### Understanding third-party Windows 10 security tools

Third-party security tools provide value and new utilities for Windows 10 desktop administrators. IT should consider ...

• ### Create an email phishing test to minimize attack vectors

With email phishing testing, IT can improve its end-user security. Phishing attacks prey on user ignorance, so IT can use a test ...

## SearchCloudComputing

• ### Estimate cloud computing costs prior to app migration

Enterprises should enlist a number of resources, including cost calculators and third-party tools, to assess what they'll pay for...

• ### Containers, cloud orchestration tools rattle DevOps foundation

Any form of virtualization that disconnects infrastructure from apps threatens the foundation of DevOps and could push IT toward ...

• ### Machine learning tools ease cloud security, log management

Machine learning has increasingly found a home in enterprise cloud management teams, but the technology is still far from being a...

## ComputerWeekly.com

• ### The importance of adopting an evergreen IT strategy

Today's modern IT systems are potentially tomorrow's legacy technology problems, without an "evergreening strategy" in place

• ### A new era of collaboration for the NHS

Great Ormond Street Hospital's new research and innovation unit, Drive, marks a significant shift towards greater collaboration ...

• ### Zeppelin uses Splunk for pre-emptive maintenance

German construction equipment rental firm Zeppelin has been using Splunk to predict when its machinery will need maintenance ...

Close