# Is there any cryptographic scheme with block size more than 128 bit

I am asking this question out of curiosity if there are any cryptographic algorithm that has a block length more that 128 bit. I am new to cryptography and I didn't know any. AES 128, 192, 256 all have same block length of 128 bit. Also if the answer is 'NO' then what can be the possible challenges of having larger block size. Thanks a lot in advanced for your help.

• The state you so-called is named block size. Rijndael later standardized as AES can use 128, 160, 192, 224, and 256 block size but only 128 is used in AES. Jul 28, 2020 at 8:33
• There may be a couple of more, here Marvin Jul 28, 2020 at 8:42
• ChaCha20 works on block (state) size of 512 bits. It is used in TLS 1.2 and 1.3. Jul 28, 2020 at 9:43
• The Ukrainian encryption standard "Kalyna" has a block size from 128 to 512 bits. Jul 28, 2020 at 12:12
• There is also Threefish. Generally the ciphers used within hash algorithms need bigger block sizes. And while we're at it, hashes and by extension HMAC's always use larger block sizes than 128 bits. So: YES. Jul 30, 2020 at 1:05

In the designs, smaller block size typically results in better implementations (though, the extent of this may vary on the paradigm and the instruction set, e.g. ARX ciphers). That is, encrypting two 64-bit blocks would be faster than encrypting one 128-bit block (with the same key size and estimated security). Roughly speaking, diffusion and confusion happen much faster.

However, 64-bit blocks have issues in modes which have birthday-bound attacks (see https://sweet32.info/ ). So 128-bit block size is the most "optimal" choice.

Taking note of comment by OP on SO, I suggest checking out IANA for encryption algorithms and cipher suites used by various Internet protocols, registered AEADs can be a good start. NIST also has a lightweight cryptography project that is on-going as of 2020.

Block ciphers rely on "mode of operation" to provide actually functional data encryption, and most mode of operations are designed for 128-bit blocks, so there's few block ciphers with bigger block size.

On the other hand, stream ciphers such as ChaCha, and its elder sister Salsa have no such restriction, and use 512-bit blocks. If you want to compare performance, RC4 may serve as a base reference.

As for the NIST LWC project, there's a report on its 1st round status.

• Many modes don't have any explicit block size inherent to the mode. CBC and CTR certainly don't, for example. Jul 30, 2020 at 20:49