What is the maximum key size for the RC5 algorithm?
A. 128 bits
B. 256 bits
C. 1024 bits
D. 2040 bits
A. 128 bits
B. 256 bits
C. 1024 bits
D. 2040 bits
Correct Answer: D
Explanation:
RC5 is a fast block cipher created by Ron Rivest and analyzed by RSA Data Security, Inc.
It is a parameterized algorithm with a variable block size, a variable key size, and a variable number of rounds.
Allowable choices for the block size are 32 bits (for experimentation and evaluation purposes only), 64 bits (for use a drop-in replacement for DES), and 128 bits.
The number of rounds can range from 0 to 255, while the key can range from 0 bits to 2040 bits in size. Please note that some sources such as the latest Shon Harris book mentions that RC5 maximum key size is of 2048, not 2040 bits. I would definitively use RSA as the authoritative source which specifies a key of 2040 bits. It is an error in Shon’s book.
The OIG book says: RC5 was developed by Ron Rivest of RSA and is deployed in many of RSA’s products. It is a very adaptable product useful for many applications, ranging from software to hardware implementations. The key for RC5 can vary from 0 to 2040 bits, the number of rounds it executes can be adjusted from 0 to 255, and the length of the input words can also be chosen from 16-, 32-, and 64-bit lengths.
The following answers were incorrect choices:
All of the other answers were wrong.
Reference(s) used for this question: Schneiter, Andrew (2013-04-15). Official (ISC)2 Guide to the CISSP CBK, Third Edition : Cryptography (Kindle Locations 10981101). . Kindle Edition.
Harris, Shon (2012-10-25). CISSP All-in-One Exam Guide, 6th Edition (Kindle Locations 16744-16747). McGraw-Hill. Kindle Edition. http://www.rsa.com/rsalabs/node.asp?id=2251, What are RC5 and RC6, RSA The Security Division of EMC. From Rivest himself, see http://people.csail.mit.edu/rivest/Rivest-rc5rev.pdf Also see the draft IETF IPSEC standard which clearly mention that it is in fact 2040 bits as a MAXIMUM key size: http://www.tools.ietf.org/html/draft-ietf-ipsec-esp-rc5-cbc-00 http://en.wikipedia.org/wiki/RC5, Mention a maximum key size of 2040 as well.
It is a parameterized algorithm with a variable block size, a variable key size, and a variable number of rounds.
Allowable choices for the block size are 32 bits (for experimentation and evaluation purposes only), 64 bits (for use a drop-in replacement for DES), and 128 bits.
The number of rounds can range from 0 to 255, while the key can range from 0 bits to 2040 bits in size. Please note that some sources such as the latest Shon Harris book mentions that RC5 maximum key size is of 2048, not 2040 bits. I would definitively use RSA as the authoritative source which specifies a key of 2040 bits. It is an error in Shon’s book.
The OIG book says: RC5 was developed by Ron Rivest of RSA and is deployed in many of RSA’s products. It is a very adaptable product useful for many applications, ranging from software to hardware implementations. The key for RC5 can vary from 0 to 2040 bits, the number of rounds it executes can be adjusted from 0 to 255, and the length of the input words can also be chosen from 16-, 32-, and 64-bit lengths.
The following answers were incorrect choices:
All of the other answers were wrong.
Reference(s) used for this question: Schneiter, Andrew (2013-04-15). Official (ISC)2 Guide to the CISSP CBK, Third Edition : Cryptography (Kindle Locations 10981101). . Kindle Edition.
Harris, Shon (2012-10-25). CISSP All-in-One Exam Guide, 6th Edition (Kindle Locations 16744-16747). McGraw-Hill. Kindle Edition. http://www.rsa.com/rsalabs/node.asp?id=2251, What are RC5 and RC6, RSA The Security Division of EMC. From Rivest himself, see http://people.csail.mit.edu/rivest/Rivest-rc5rev.pdf Also see the draft IETF IPSEC standard which clearly mention that it is in fact 2040 bits as a MAXIMUM key size: http://www.tools.ietf.org/html/draft-ietf-ipsec-esp-rc5-cbc-00 http://en.wikipedia.org/wiki/RC5, Mention a maximum key size of 2040 as well.