Technology

The American National Institute for Standards and Technology (NIST) is rather busy on the cryptographic front these days. Not only has it been busy in the area of Post-Quantum Cryptography (PQC), it is also in the process of standardizing the lightweight cipher Ascon, and it is also embarking soon on a major effort to examine threshold cryptography, but in late 2024 it announced that it would be looking at standardizing a larger block size variant of the AES algorithm.

To understand what this proposal is, and why it is important, we need to dig a bit deeper into what a block cipher is, and the history of the AES algorithm.

Block ciphers explained

A block cipher is a mechanism to encrypt single blocks of data using a secret key. The two important characteristics of a block cipher are the number of bits needed to determine the key (the so-called key size) and the size of the data which each application of the block cipher encrypts (the co-called block size).

Children often encounter block ciphers as a first introduction to cryptography by making a table of letters, and then placing a random permutation of the letters underneath them such as

A - B - C - D - E - F - G - H - I - J - K - L - M

T - M- A - H - X - S - C - Q - N - R - P - D -E

So the word BAD would encrypt to the ciphertext MTH. In this example the key is the second row of the table (you need the second row to encrypt and decrypt). This gives a total number of keys of

26 · 25 · 24 ··· 3 · 2 · 1 ≈ 2 88.3

which corresponds to a key size of 88.3 bits. The block size is however only one letter, i.e. something which can be represented in bits. This key size is quite large, if I just gave you an encrypted message of three letters it would be hard to determine the key.

However, because the block size is small it is easy to break in practice, since a large encrypted text will reveal repeats of plaintext blocks. For example the words “HIDE ME” will encrypt to “QNHX EX”, and we can see the repetition of X encrypting E. As we know E is the most likely letter in English this means it is likely that the attacker can guess X encrypts E.

Even if we were encrypting random messages (and not English) this repetition of blocks is a way for an attacker to attack any system which uses the block cipher. Due to the birthday paradox, if we have a block size of b bits, then we expect such a collision to after a few blocks. For the case of our toy cipher this means, for a random message, we expect a collision to occur after about 5 blocks.

AES

AES is a block cipher, which is the workhorse of almost all cryptographic systems in the world today. It was standardized by NIST in 2001, and has a variable key size of 128, 192 and 256 bits, but a fixed block size of 128 bits. This fixing of the block size was not originally on the cards.

In the original preliminary call for AES, NIST proposed having 128, 192 and 256 bit key sizes, with a fixed block size of 128-bits, but with the option for other block sizes.

However, as the process to choose AES progressed, in the official first call in 1997 NIST decided to focus only on 128 bit block sizes. In 2001 this block size seemed alright. After all, it means that for a random message we only expect to output blocks to be identical after ciphertext blocks, or 256 Exabytes.

The problem is that this “seemed alright” was not quite true. AES was actually based on an algorithm called Rijndael (invented by two Belgian mathematicians called Joan Daemen and Vincent Rijmen). In its original design, submitted to NIST, Rijndael had three possible key sizes (128, 192 and 256 bits) and three possible block sizes (128, 192 and 256 bits).

As we just remarked, during the AES process, in order to simplify the competition, NIST decided that it would only focus on 128-bit block sizes. Thus the original Rijndael design was modified to only allow one block size.

Unfortunate consequences

The fact that collisions happen more likely with a smaller block size means that applications needed to limit the number of blocks they could encrypt. This means that we only use a single 128-bit key to encrypt a relatively small amount of data. In practice this limit on the amount one can encrypt with one key becomes blocks, or only 64 Gigabytes (which is less than most harddisks in a laptop these days) , when AES is used in its most popular scenario (called AES-GCM mode). Meaning we need to rekey our ciphers more often, or use another method of calling AES.

Due to AES being super fast in hardware it would be good if we could use AES to construct a hash function (which are very slow normally). One can use block ciphers to construct hash functions, but they are not very secure (or are more complex to construct) unless the block cipher has a big block size (such as 256 bits).

The mismatch between block size and key size for the AES algorithm led to a theoretical “attack” (in a very special situation) on the AES algorithm with 256 bit key size in 2009 due to Biryukov and Khovratovich. Thus AES-256, with its 128-bit block size, was not as good as one would expect. On the other hand using Rijndael with 256-bit key and 256- bit block size would have avoided this “attack”.

Summary

Thus what NIST has announced is to revisit, what in hindsight, was the mistake it made back in 2001. AES should really have been standardized with a 256 bit block size variant.

If cryptographers had a DeLorean time machine they would go back about twenty five years, and modify the AES competition so that the final decision would have allowed AES to be used with a 256-bit block size.

We've compiled a list of the best encryption software.

This article was produced as part of TechRadarPro's Expert Insights channel where we feature the best and brightest minds in the technology industry today. The views expressed here are those of the author and are not necessarily those of TechRadarPro or Future plc. If you are interested in contributing find out more here: https://www.techradar.com/news/submit-your-story-to-techradar-pro

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Celebrity Big Brother is back, with another set of familiar faces looking to stick out the UK version of television's original social experiment to its end. UK viewers can catch daily episodes live and on demand on the free-to-air ITV and ITVX services, and if you're away, you can watch Celebrity Big Brother 2025 online from anywhere with a VPN.

AJ Odudu and Will Best are back on hosting duties for the 24th edition of the celebrity-based shenanigans and Monday's launch episode saw the 13 contestants enter the house – you can see a full list at the bottom of this article.

This year's main attraction is Oscar-nominated actor Mickey Rourke, with the Hollywood star intermingling with the likes of the unlikely best chums RuPaul's Drag Race UK's Danny Beard and bouffant-haired former MP Michael Fabricant. Joining them are one-hit-wonder Chesney Hawkes, Eastenders legend Patsy Palmer and double Olympic champion Daley Thompson, with Love Island's Chris Hughes looking like an early favorite.

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Below we’ve got all the information on where to watch Celebrity Big Brother 2025 online and stream every episode from wherever you are.

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Viewers in the UK can watch series 24 of Celebrity Big Brother completely FREE on ITV1 on TV and its ITVX streaming service online.

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• The new emojis come at the same time as iOS 18.4's Ambient Music feature and new Photos tool
• Since being released, users have taken to the new additions well, especially Apple's new smiley emoji

It’s been a week since Apple released its latest iOS 18.4 update, and despite its rather rocky rollout of Apple Intelligence, the new software update packs some redeeming features - one of them being the addition of eight new emojis.

Apple’s library of emojis is extensive to say the very least, offering small visual elements that iPhone users including myself rely on to bring a text message or group chat to life.

Although the company has introduced only eight new ones, each is unique, and there’s one in particular that’s far too relatable. It’s easily the best one of the bunch.

Yes, new emojis are the most basic feature iOS 18.4 introduces – it also brings a new Photos tool and Ambient Music feature – but that doesn’t mean we’re not allowed to be excited about them.

I’ve had a real hard look at the eight new additions to Apple’s range of emojis and already I know which ones I’ll be using the most, and the ones I could do without - here’s my verdict.

8. Root vegetable

(Image credit: Unicode / Emojipedia)

Is it a turnip? Is it a radish? I don’t know. But what I do know is that this is the emoji I will be using the least. There are enough food emojis out there already, so what impact is this one having?

7. Bare tree

(Image credit: Unicode / Emojipedia)

I use Apple's nature emojis quite often, especially when captioning a photo with a picturesque natural landscape or quirky plant. The new bare tree emoji just looks a little sad, though.

The only instance where I would maybe use this is during autumn or even Halloween, but it’s not one I’m itching to use right now.

6. Spade/ shovel

(Image credit: Unicode / Emojipedia)

Let’s call a spade a spade. This one is on the more boring side of Apple’s iOS 18.4 emojis. If you have a particular attachment to spades or shovels, then perhaps you’ll find yourself visiting this emoji over and over. For me, not so much.

5. Flag of Sark

(Image credit: Unicode / Emojipedia)

Like most flag emojis, you’d only use them in very specific contexts or if you’re expressing national pride (I use the Welsh flag emoji constantly). That aside, it’s a pretty neat-looking flag, and it's nice to see Apple bring more national flags to its library.

4. Splatter

(Image credit: Unicode / Emojipedia)

From its design, the purple splatter emoji is another one that I would’ve thought was always part of the emoji gallery. But alas, it’s shiny and new.

This is another one that looks good, but the only thing that lets it down is the lack of different color options, which would entice me to use it more.

Perhaps the next iOS update will fix this?

3. Fingerprint

(Image credit: Unicode / Emojipedia)

The fingerprint emoji is just cool to look at. Is it as exciting as the new smiley emoji? I wouldn’t say so, but design-wise, it still packs a punch and is a solid addition to the emoji library.

2. Harp

(Image credit: Unicode / Emojipedia)

It’s strange that a harp emoji is one of the new additions to iOS 18.4 because I would’ve assumed that this was always there. That shows how often I use musical instrument emojis.

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(Image credit: Unicode / Emojipedia)

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Since iOS 18.4 was released, this emoji has received a lot of praise from Apple users for the reason above alone. This shows that relatability is everything when it comes to emojis, and there’s no doubt this one will be a hit with users.

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There's been a lot of discussion about the price of the Nintendo Switch 2 and now the Nintendo of America president has chimed in.

Some, including several notable industry analysts, have speculated that the $429.99 / £395.99 starting price was decided with potential US tariffs in mind.

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Bowser added that "the new [of the tariffs] is fresh, and like many companies right now, [Nintendo] are actively assessing what the impact may be."

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