ISC SSCP Exam Made Easy: Step-by-Step Preparation Guide

Source: TIPTON, Hal, (ISC)2, Introduction to the CISSP Exam presentation.

Output feedback (OFB) is a DES mode of operation, not input feedback.

Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 4: Cryptography (page 149).

As protocol was introduced by Visa and Mastercard to allow for more credit card transaction possibilities. It is comprised of three different pieces of software, running on the customer's PC (an electronic wallet), on the merchant's Web server and on the payment server of the merchant's bank. The credit card information is sent by the customer to the merchant's Web server, but it does not open it and instead digitally signs it and sends it to its bank's payment server for processing.

The following answers are incorrect because :

SSH (Secure Shell) is incorrect as it functions as a type of tunneling mechanism that provides terminal like access to remote computers.

S/MIME is incorrect as it is a standard for encrypting and digitally signing electronic mail and for providing secure data transmissions.

SSL is incorrect as it uses public key encryption and provides data encryption, server authentication, message integrity, and optional client authentication.

Reference : Shon Harris AIO v3 , Chapter-8: Cryptography , Page : 667-669

In a ciphertext-only attack, the attacker has the ciphertext of several messages encrypted with the same encryption algorithm. Its goal is to discover the plaintext of the messages by figuring out the key used in the encryption process. In a known-plaintext attack, the attacker has the plaintext and the ciphertext of one or more messages. In a chosen-ciphertext attack, the attacker can chose the ciphertext to be decrypted and has access to the resulting plaintext.

Source: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, Chapter 8: Cryptography (page 578).

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 1098-1101). . 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.

The security of the RSA system is based on the assumption that factoring the product into two original large prime numbers is difficult

Source:

KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 4: Cryptography (page 159).

Shon Harris, CISSP All-in-One Examine Guide, Third Edition, McGraw-Hill Companies, August 2005, Chapter 8: Cryptography, Page 636 - 639

When we encrypt messages using our private keys which are only available to us. The person who wants to read and decrypt the message need only have our public keys to do so.

The whole point to PKI is to assure message integrity, authentication of the source, and to provide secrecy with the digital encryption.

See below a nice walktrough of Digital Signature creation and verification from the Comodo web site:

Digital Signatures apply the same functionality to an e-mail message or data file that a handwritten signature does for a paper-based document. The Digital Signature vouches for the origin and integrity of a message, document or other data file.

How do we create a Digital Signature?

The creation of a Digital Signature is a complex mathematical process. However as the complexities of the process are computed by the computer, applying a Digital Signature is no more difficult that creating a handwritten one!

The following text illustrates in general terms the processes behind the generation of a Digital Signature:

1. Alice clicks 'sign' in her email application or selects which file is to be signed.

2. Alice's computer calculates the 'hash' (the message is applied to a publicly known mathematical hashing function that coverts the message into a long number referred to as the hash).

3. The hash is encrypted with Alice's Private Key (in this case it is known as the Signing Key) to create the Digital Signature.

4. The original message and its Digital Signature are transmitted to Bob.

5. Bob receives the signed message. It is identified as being signed, so his email application knows which actions need to be performed to verify it.

6. Bob's computer decrypts the Digital Signature using Alice's Public Key.

7. Bob's computer also calculates the hash of the original message (remember - the mathematical function used by Alice to do this is publicly known).

8. Bob's computer compares the hashes it has computed from the received message with the now decrypted hash received with Alice's message.

digital signature creation and verification

If the message has remained integral during its transit (i.e. it has not been tampered with), when compared the two hashes will be identical.

However, if the two hashes differ when compared then the integrity of the original message has been compromised. If the original message is tampered with it will result in Bob's computer calculating a different hash value. If a different hash value is created, then the original message will have been altered. As a result the verification of the Digital Signature will fail and Bob will be informed.

Origin, Integrity, Non-Repudiation, and Preventing Men-In-The-Middle (MITM) attacks

Eve, who wants to impersonate Alice, cannot generate the same signature as Alice because she does not have Alice's Private Key (needed to sign the message digest). If instead, Eve decides to alter the content of the message while in transit, the tampered message will create a different message digest to the original message, and Bob's computer will be able to detect that. Additionally, Alice cannot deny sending the message as it has been signed using her Private Key, thus ensuring non-repudiation.

creating and validating a digital signature

Due to the recent Global adoption of Digital Signature law, Alice may now sign a transaction, message or piece of digital data, and so long as it is verified successfully it is a legally permissible means of proof that Alice has made the transaction or written the message.

The following answers are incorrect:

- Public / Private: This is the opposite of the right answer.

- Symmetric / Asymmetric: Not quite. Sorry. This form of crypto is asymmetric so you were almost on target.

- Private / Symmetric: Well, you got half of it right but Symmetric is wrong.

The following reference(s) was used to create this question:

The CCCure Holistic Security+ CBT, you can subscribe at: http://www.cccure.tv

and

http://www.comodo.com/resources/small-business/digital-certificates3.php

RFC 2828 (Internet Security Glossary) defines digital watermarking as computing techniques for inseparably embedding unobtrusive marks or labels as bits in digital data-text, graphics, images, video, or audio#and for detecting or extracting the marks later. The set of embedded bits (the digital watermark) is sometimes hidden, usually imperceptible, and always intended to be unobtrusive. It is used as a measure to protect intellectual property rights. Steganography involves hiding the very existence of a message. A digital signature is a value computed with a cryptographic algorithm and appended to a data object in such a way that any recipient of the data can use the signature to verify the data's origin and integrity. A digital envelope is a combination of encrypted data and its encryption key in an encrypted form that has been prepared for use of the recipient.

Source: SHIREY, Robert W., RFC2828: Internet Security Glossary, may 2000.

The Internet Security Glossary (RFC2828) defines the Authority Revocation List (ARL) as a data structure that enumerates digital certificates that were issued to CAs but have been invalidated by their issuer prior to when they were scheduled to expire.

Do not to confuse with an ARL with a Certificate Revocation List (CRL). A certificate revocation list is a mechanism for distributing notices of certificate revocations. The question specifically mentions "issued to CAs" which makes ARL a better answer than CRL.

http://rfclibrary.hosting.com/rfc/rfc2828/rfc2828-29.asp

$ certificate revocation list (CRL)

(I) A data structure that enumerates digital certificates that have been invalidated by their issuer prior to when they were

scheduled to expire. (See: certificate expiration, X.509 certificate revocation list.)

http://rfclibrary.hosting.com/rfc/rfc2828/rfc2828-17.asp

$ authority revocation list (ARL)

(I) A data structure that enumerates digital certificates that were issued to CAs but have been invalidated by their issuer prior to when they were scheduled to expire. (See: certificate expiration, X.509 authority revocation list.)

In a few words: We use CRL's for end-user cert revocation and ARL's for CA cert revocation - both can be placed in distribution points.

Remember the term Public-Key Certificate is synonymous with Digital Certificate or Identity certificate.

The certificate itself provides the binding but it is the certificate authority who will go through the Certificate Practice Statements (CPS) actually validating the bindings and vouch for the identity of the owner of the key within the certificate.

As explained in Wikipedia:

In cryptography, a public key certificate (also known as a digital certificate or identity certificate) is an electronic document which uses a digital signature to bind together a public key with an identity — information such as the name of a person or an organization, their address, and so forth. The certificate can be used to verify that a public key belongs to an individual.

In a typical public key infrastructure (PKI) scheme, the signature will be of a certificate authority (CA). In a web of trust scheme such as PGP or GPG, the signature is of either the user (a self-signed certificate) or other users ("endorsements") by getting people to sign each other keys. In either case, the signatures on a certificate are attestations by the certificate signer that the identity information and the public key belong together.

RFC 2828 defines the certification authority (CA) as:

An entity that issues digital certificates (especially X.509 certificates) and vouches for the binding between the data items in a certificate.

An authority trusted by one or more users to create and assign certificates. Optionally, the certification authority may create the user's keys.

X509 Certificate users depend on the validity of information provided by a certificate. Thus, a CA should be someone that certificate users trust, and usually holds an official position created and granted power by a government, a corporation, or some other organization. A CA is responsible for managing the life cycle of certificates and, depending on the type of certificate and the CPS that applies, may be responsible for the life cycle of key pairs associated with the certificates

Source: SHIREY, Robert W., RFC2828: Internet Security Glossary, may 2000.

and

http://en.wikipedia.org/wiki/Public_key_certificate

The following are incorrect answers because they are all suitable methods.

A Delta CRL is a CRL that only provides information about certificates whose statuses have changed since the issuance of a specific, previously issued CRL.

The Online Certificate Status Protocol (OCSP) is an Internet protocol used for obtaining the revocation status of an X.509 digital certificate.

A Distribution point CRL or CRL Distribution Point, a location specified in the CRL Distribution Point (CRL DP) X.509, version 3, certificate extension when the certificate is issued.

References:

RFC 2459: Internet X.509 Public Key Infrastru

http://csrc.nist.gov/groups/ST/crypto_apps_infra/documents/sliding_window.pdf

http://www.ipswitch.eu/online_certificate_status_protocol_en.html

Computer Security Handbook By Seymour Bosworth, Arthur E. Hutt, Michel E. Kabay http://books.google.com/books?id=rCx5OfSFUPkC &printsec=frontcover&dq=Computer+Security+Handbook#PRA6-PA4,M1

References: RFC 2459 : Internet X.509 Public Key Infrastructure Certificate and CRL Profile; GUTMANN, P., X.509 style guide.

In cryptography, the one-time pad (OTP) is a type of encryption that is impossible to crack if used correctly. Each bit or character from the plaintext is encrypted by a modular addition with a bit or character from a secret random key (or pad) of the same length as the plaintext, resulting in a ciphertext. If the key is truly random, at least as long as the plaintext, never reused in whole or part, and kept secret, the ciphertext will be impossible to decrypt or break without knowing the key. It has also been proven that any cipher with the perfect secrecy property must use keys with effectively the same requirements as OTP keys. However, practical problems have prevented one-time pads from being widely used.

First described by Frank Miller in 1882, the one-time pad was re-invented in 1917 and patented a couple of years later. It is derived from the Vernam cipher, named after Gilbert Vernam, one of its inventors. Vernam's system was a cipher that combined a message with a key read from a punched tape. In its original form, Vernam's system was vulnerable because the key tape was a loop, which was reused whenever the loop made a full cycle. One-time use came a little later when Joseph Mauborgne recognized that if the key tape were totally random, cryptanalysis would be impossible.

The "pad" part of the name comes from early implementations where the key material was distributed as a pad of paper, so the top sheet could be easily torn off and destroyed after use. For easy concealment, the pad was sometimes reduced to such a small size that a powerful magnifying glass was required to use it. Photos show captured KGB pads that fit in the palm of one's hand, or in a walnut shell. To increase security, one-time pads were sometimes printed onto sheets of highly flammable nitrocellulose so they could be quickly burned.

The following are incorrect answers:

A running key cipher uses articles in the physical world rather than an electronic algorithm. In classical cryptography, the running key cipher is a type of polyalphabetic substitution cipher in which a text, typically from a book, is used to provide a very long keystream. Usually, the book to be used would be agreed ahead of time, while the passage to use would be chosen randomly for each message and secretly indicated somewhere in the message.

The Running Key cipher has the same internal workings as the Vigenere cipher. The difference lies in how the key is chosen; the Vigenere cipher uses a short key that repeats, whereas the running key cipher uses a long key such as an excerpt from a book. This means the key does not repeat, making cryptanalysis more difficult. The cipher can still be broken though, as there are statistical patterns in both the key and the plaintext which can be exploited.

Steganography is a method where the very existence of the message is concealed. It is the art and science of encoding hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message. it is sometimes referred to as Hiding in Plain Sight.

Cipher block chaining is a DES operating mode. IBM invented the cipher-block chaining (CBC) mode of operation in 1976. In CBC mode, each block of plaintext is XORed with the previous ciphertext block before being encrypted. This way, each ciphertext block depends on all plaintext blocks processed up to that point. To make each message unique, an initialization vector must be used in the first block.

Reference(s) used for this question:

HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, chapter 8: Cryptography (page 555).

and

http://en.wikipedia.org/wiki/One-time_pad

http://en.wikipedia.org/wiki/Running_key_cipher

http://en.wikipedia.org/wiki/Cipher_block_chaining#Cipher-block_chaining_.28CBC.29

In a known plaintext attack, the attacker has the plaintext and ciphertext of one or more messages. The goal is to discover the key used to encrypt the messages so that other messages can be deciphered and read.

Source: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 3rd Ed., chapter 8: Cryptography (page 676). Also check out: Handbook of Applied Cryptography 4th Edition by Alfred J. Menezes, Paul C. van Oorschot and Scott A. Vanstone.

A digital envelope for a recipient is a combination of encrypted data and its encryption key in an encrypted form that has been prepared for use of the recipient.

It consists of a hybrid encryption scheme in sealing a message, by encrypting the data and sending both it and a protected form of the key to the intended recipient, so that one else can open the message.

In PKCS #7, it means first encrypting the data using a symmetric encryption algorithm and a secret key, and then encrypting the secret key using an asymmetric encryption algorithm and the public key of the intended recipient.

Source: SHIREY, Robert W., RFC2828: Internet Security Glossary, may 2000.

As session key is a symmetric key that is used to encrypt messages between two users. A session key is only good for one communication session between users.

For example , If Tanya has a symmetric key that she uses to encrypt messages between Lance and herself all the time , then this symmetric key would not be regenerated or changed. They would use the same key every time they communicated using encryption. However , using the same key repeatedly increases the chances of the key being captured and the secure communication being compromised. If , on the other hand , a new symmetric key were generated each time Lance and Tanya wanted to communicate , it would be used only during their dialog and then destroyed. if they wanted to communicate and hour later , a new session key would be created and shared.

The other answers are not correct because :

Public Key can be known to anyone.

Private Key must be known and used only by the owner.

Secret Keys are also called as Symmetric Keys, because this type of encryption relies on each user to keep the key a secret and properly protected.

REFERENCES:

SHON HARRIS , ALL IN ONE THIRD EDITION : Chapter 8 : Cryptography , Page : 619-620

RC4 was designed by Ron Rivest of RSA Security in 1987. While it is officially termed "Rivest Cipher 4", the RC acronym is alternatively understood to stand for "Ron's Code" (see also RC2, RC5 and RC6).

RC4 was initially a trade secret, but in September 1994 a description of it was anonymously posted to the Cypherpunks mailing list. It was soon posted on the sci.crypt newsgroup, and from there to many sites on the Internet. The leaked code was confirmed to be genuine as its output was found to match that of proprietary software using licensed RC4. Because the algorithm is known, it is no longer a trade secret. The name RC4 is trademarked, so RC4 is often referred to as ARCFOUR or ARC4 (meaning alleged RC4) to avoid trademark problems. RSA Security has never officially released the algorithm; Rivest has, however, linked to the English Wikipedia article on RC4 in his own course notes. RC4 has become part of some commonly used encryption protocols and standards, including WEP and WPA for wireless cards and TLS.

The main factors in RC4's success over such a wide range of applications are its speed and simplicity: efficient implementations in both software and hardware are very easy to develop.

The following answer were not correct choices:

SHA-1 is a one-way hashing algorithms. SHA-1 is a cryptographic hash function designed by the United States National Security Agency and published by the United States NIST as a U.S. Federal Information Processing Standard. SHA stands for "secure hash algorithm".

The three SHA algorithms are structured differently and are distinguished as SHA-0, SHA-1, and SHA-2. SHA-1 is very similar to SHA-0, but corrects an error in the original SHA hash specification that led to significant weaknesses. The SHA-0 algorithm was not adopted by many applications. SHA-2 on the other hand significantly differs from the SHA-1 hash function.

SHA-1 is the most widely used of the existing SHA hash functions, and is employed in several widely used security applications and protocols. In 2005, security flaws were identified in SHA-1, namely that a mathematical weakness might exist, indicating that a stronger hash function would be desirable. Although no successful attacks have yet been reported on the SHA-2 variants, they are algorithmically similar to SHA-1 and so efforts are underway to develop improved alternatives. A new hash standard, SHA-3, is currently under development — an ongoing NIST hash function competition is scheduled to end with the selection of a winning function in 2012.

SHA-1 produces a 160-bit message digest based on principles similar to those used by Ronald L. Rivest of MIT in the design of the MD4 and MD5 message digest algorithms, but has a more conservative design.

MD2 is a one-way hashing algorithms. The MD2 Message-Digest Algorithm is a cryptographic hash function developed by Ronald Rivest in 1989. The algorithm is optimized for 8-bit computers. MD2 is specified in RFC 1319. Although MD2 is no longer considered secure, even as of 2010 it remains in use in public key infrastructures as part of certificates generated with MD2 and RSA.

Haval is a one-way hashing algorithms. HAVAL is a cryptographic hash function. Unlike MD5, but like most modern cryptographic hash functions, HAVAL can produce hashes of different lengths. HAVAL can produce hashes in lengths of 128 bits, 160 bits, 192 bits, 224 bits, and 256 bits. HAVAL also allows users to specify the number of rounds (3, 4, or 5) to be used to generate the hash.

The following reference(s) were used for this question:

SHIREY, Robert W., RFC2828: Internet Security Glossary, may 2000.

and

https://en.wikipedia.org/wiki/HAVAL

and

https://en.wikipedia.org/wiki/MD2_%28cryptography%29

and

https://en.wikipedia.org/wiki/SHA-1

In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence.

The encryption step performed by a Caesar cipher is often incorporated as part of more complex schemes, such as the Vigenère cipher, and still has modern application in the ROT13 system. As with all single alphabet substitution ciphers, the Caesar cipher is easily broken and in modern practice offers essentially no communication security.

The following answer were incorrect:

The Jefferson disk, or wheel cipher as Thomas Jefferson named it, also known as the Bazeries Cylinder, is a cipher system using a set of wheels or disks, each with the 26 letters of the alphabet arranged around their edge. The order of the letters is different for each disk and is usually scrambled in some random way. Each disk is marked with a unique number. A hole in the centre of the disks allows them to be stacked on an axle. The disks are removable and can be mounted on the axle in any order desired. The order of the disks is the cipher key, and both sender and receiver must arrange the disks in the same predefined order. Jefferson's device had 36 disks.

An Enigma machine is any of a family of related electro-mechanical rotor cipher machines used for the encryption and decryption of secret messages. Enigma was invented by the German engineer Arthur Scherbius at the end of World War I. The early models were used commercially from the early 1920s, and adopted by military and government services of several countries. Several different Enigma models were produced, but the German military models are the ones most commonly discussed.

SIGABA: In the history of cryptography, the ECM Mark II was a cipher machine used by the United States for message encryption from World War II until the 1950s. The machine was also known as the SIGABA or Converter M-134 by the Army, or CSP-888/889 by the Navy, and a modified Navy version was termed the CSP-2900. Like many machines of the era it used an electromechanical system of rotors in order to encipher messages, but with a number of security improvements over previous designs. No successful cryptanalysis of the machine during its service lifetime is publicly known.

Reference(s) used for this question:

http://en.wikipedia.org/wiki/Jefferson_disk

http://en.wikipedia.org/wiki/Sigaba

http://en.wikipedia.org/wiki/Enigma_machine

RFC 2828 (Internet Security Glossary) defines Simple Key Management for Internet Protocols (SKIP) as:

A key distribution protocol that uses hybrid encryption to convey session keys that are used to encrypt data in IP packets.

SKIP is an hybrid Key distribution protocol similar to SSL, except that it establishes a long-term key once, and then requires no prior communication in order to establish or exchange keys on a session-by-session basis. Therefore, no connection setup overhead exists and new keys values are not continually generated. SKIP uses the knowledge of its own secret key or private component and the destination's public component to calculate a unique key that can only be used between them.

IKE stand for Internet Key Exchange, it makes use of ISAKMP and OAKLEY internally.

Internet Key Exchange (IKE or IKEv2) is the protocol used to set up a security association (SA) in the IPsec protocol suite. IKE builds upon the Oakley protocol and ISAKMP. IKE uses X.509 certificates for authentication and a Diffie–Hellman key exchange to set up a shared session secret from which cryptographic keys are derived.

The following are incorrect answers:

ISAKMP is an Internet IPsec protocol to negotiate, establish, modify, and delete security associations, and to exchange key generation and authentication data, independent of the details of any specific key generation technique, key establishment protocol, encryption algorithm, or authentication mechanism.

IKE is an Internet, IPsec, key-establishment protocol (partly based on OAKLEY) that is intended for putting in place authenticated keying material for use with ISAKMP and for other security associations, such as in AH and ESP.

IPsec Key exchange (IKE) is only a detracto.

Reference(s) used for this question:

SHIREY, Robert W., RFC2828: Internet Security Glossary, may 2000.

and

http://en.wikipedia.org/wiki/Simple_Key-Management_for_Internet_Protocol

and

http://en.wikipedia.org/wiki/Simple_Key-Management_for_Internet_Protocol