Block Cipher Clarification

g33k3r

I am creating my study notes and wanted to make sure I understand this concept correctly.

Pardon the simplified definition but I am trying to put this in my own words.

Block Ciphers encrypt data in "blocks"/chunks. The size of the block depends on the algorithm used. For example, DES has a block size of 64 bit. Data is encrypted in 64 bit blocks using a 56 bit key 16 times (rounds).

Thanks!

gespenstern

Sounds okay. However, AFAIR key size for DES is 64 bit. Effective key size is 56 and the rest is padded with something.

g33k3r

Gespenstern, you are correct:

"DES actually has a key length of 64 bits, however 8 bits are used for parity, therefore the effective key length is 56 bits."

Thanks for chiming in. Learned something new today!

!nf0s3cure

I read on one feedback from the exam that there was nothing asked about Crypto. I'd be happy with that. I'd rather see more questions on securing systems in current scenario.

Anyway a good read for benefit of all...Goodbye DES, Welcome AES - The Internet Protocol Journal - Volume 4, Number 2 - Cisco Systems

cbkihong

I was asked about one of the crypto attacks on my exam though. I studied that but was just a bit surprised it was asked.

g33k3r

!nf0s3cure wrote: »

I read on one feedback from the exam that there was nothing asked about Crypto. I'd be happy with that. I'd rather see more questions on securing systems in current scenario.

Anyway a good read for benefit of all...Goodbye DES, Welcome AES - The Internet Protocol Journal - Volume 4, Number 2 - Cisco Systems

Seriously?? I am basing my study notes on the old 10 domain guides. So far crypto is my largest section of notes!

!nf0s3cure

I am sure it was here on TE a few weeks after the revised domains!