SSCP : System Security Certified Practitioner (SSCP) : Part 03

SSCP : System Security Certified Practitioner (SSCP) : Part 03

  1. Which of the following is a cryptographic protocol and infrastructure developed to send encrypted credit card numbers over the Internet?

    • Secure Electronic Transaction (SET)
    • MONDEX
    • Secure Shell (SSH-2)
    • Secure Hypertext Transfer Protocol (S-HTTP)

    Explanation:

    SET was developed by a consortium including Visa and MasterCard.
    Source: Harris, Shon, CISSP All In One Exam Guide, pages 668-669.

    Mondex is a smart card electronic cash system owned by MasterCard.
    SSH-2 is a secure, efficient, and portable version of SSH (Secure Shell) which is a secure replacement for telnet.

    Secure HTTP is a secure message-oriented communications protocol designed for use in conjunction with HTTP. It is designed to coexist with HTTP’s messaging model and to be easily integrated with HTTP applications.

  2. Which of the following cryptographic attacks describes when the attacker has a copy of the plaintext and the corresponding ciphertext?

    • known plaintext
    • brute force
    • ciphertext only
    • chosen plaintext
    Explanation:

    The goal to this type of attack is to find the cryptographic key that was used to encrypt the message. Once the key has been found, the attacker would then be able to decrypt all messages that had been encrypted using that key.

    The known-plaintext attack (KPA) or crib is an attack model for cryptanalysis where the attacker has samples of both the plaintext and its encrypted version (ciphertext), and is at liberty to make use of them to reveal further secret information such as secret keys and code books. The term “crib” originated at Bletchley Park, the British World War II decryption operation

    In cryptography, a brute force attack or exhaustive key search is a strategy that can in theory be used against any encrypted data by an attacker who is unable to take advantage of any weakness in an encryption system that would otherwise make his task easier. It involves systematically checking all possible keys until the correct key is found. In the worst case, this would involve traversing the entire key space, also called search space.

    In cryptography, a ciphertext-only attack (COA) or known ciphertext attack is an attack model for cryptanalysis where the attacker is assumed to have access only to a set of ciphertexts.

    The attack is completely successful if the corresponding plaintexts can be deduced, or even better, the key. The ability to obtain any information at all about the underlying plaintext is still considered a success. For example, if an adversary is sending ciphertext continuously to maintain traffic-flow security, it would be very useful to be able to distinguish real messages from nulls. Even making an informed guess of the existence of real messages would facilitate traffic analysis.

    In the history of cryptography, early ciphers, implemented using pen-and-paper, were routinely broken using ciphertexts alone. Cryptographers developed statistical techniques for attacking ciphertext, such as frequency analysis. Mechanical encryption devices such as Enigma made these attacks much more difficult (although, historically, Polish cryptographers were able to mount a successful ciphertext-only cryptanalysis of the Enigma by exploiting an insecure protocol for indicating the message settings).

    Every modern cipher attempts to provide protection against ciphertext-only attacks. The vetting process for a new cipher design standard usually takes many years and includes exhaustive testing of large quantities of ciphertext for any statistical departure from random noise. See: Advanced Encryption Standard process. Also, the field of steganography evolved, in part, to develop methods like mimic functions that allow one piece of data to adopt the statistical profile of another. Nonetheless poor cipher usage or reliance on home-grown proprietary algorithms that have not been subject to thorough scrutiny has resulted in many computer-age encryption systems that are still subject to ciphertext-only attack. Examples include:

    Early versions of Microsoft’s PPTP virtual private network software used the same RC4 key for the sender and the receiver (later versions had other problems). In any case where a stream cipher like RC4 is used twice with the same key it is open to ciphertext-only attack. See: stream cipher attack
    Wired Equivalent Privacy (WEP), the first security protocol for Wi-Fi, proved vulnerable to several attacks, most of them ciphertext-only.

    A chosen-plaintext attack (CPA) is an attack model for cryptanalysis which presumes that the attacker has the capability to choose arbitrary plaintexts to be encrypted and obtain the corresponding ciphertexts. The goal of the attack is to gain some further information which reduces the security of the encryption scheme. In the worst case, a chosen-plaintext attack could reveal the scheme’s secret key.

    This appears, at first glance, to be an unrealistic model; it would certainly be unlikely that an attacker could persuade a human cryptographer to encrypt large amounts of plaintexts of the attacker’s choosing. Modern cryptography, on the other hand, is implemented in software or hardware and is used for a diverse range of applications; for many cases, a chosen-plaintext attack is often very feasible. Chosen-plaintext attacks become extremely important in the context of public key cryptography, where the encryption key is public and attackers can encrypt any plaintext they choose.

    Any cipher that can prevent chosen-plaintext attacks is then also guaranteed to be secure against known-plaintext and ciphertext-only attacks; this is a conservative approach to security.

    Two forms of chosen-plaintext attack can be distinguished:

    Batch chosen-plaintext attack, where the cryptanalyst chooses all plaintexts before any of them are encrypted. This is often the meaning of an unqualified use of “chosen-plaintext attack”.

    Adaptive chosen-plaintext attack, where the cryptanalyst makes a series of interactive queries, choosing subsequent plaintexts based on the information from the previous encryptions.

    References:
    Source: TIPTON, Harold, Official (ISC)2 Guide to the CISSP CBK (2007), page 271.
    and
    Wikipedia at the following links:
    http://en.wikipedia.org/wiki/Chosen-plaintext_attack
    http://en.wikipedia.org/wiki/Known-plaintext_attack
    http://en.wikipedia.org/wiki/Ciphertext-only_attack
    http://en.wikipedia.org/wiki/Brute_force_attack

  3. The primary purpose for using one-way hashing of user passwords within a password file is which of the following?

    • It prevents an unauthorized person from trying multiple passwords in one logon attempt.
    • It prevents an unauthorized person from reading the password.
    • It minimizes the amount of storage required for user passwords.
    • It minimizes the amount of processing time used for encrypting passwords.
    Explanation:

    The whole idea behind a one-way hash is that it should be just that – one-way. In other words, an attacker should not be able to figure out your password from the hashed version of that password in any mathematically feasible way (or within any reasonable length of time).

    Password Hashing and Encryption
    In most situations , if an attacker sniffs your password from the network wire, she still has some work to do before she actually knows your password value because most systems hash the password with a hashing algorithm, commonly MD4 or MD5, to ensure passwords are not sent in cleartext.

    Although some people think the world is run by Microsoft, other types of operating systems are out there, such as Unix and Linux. These systems do not use registries and SAM databases, but contain their user passwords in a file cleverly called “shadow.” Now, this shadow file does not contain passwords in cleartext; instead, your password is run through a hashing algorithm, and the resulting value is stored in this file.

    Unixtype systems zest things up by using salts in this process. Salts are random values added to the encryption process to add more complexity and randomness. The more randomness entered into the encryption process, the harder it is for the bad guy to decrypt and uncover your password. The use of a salt means that the same password can be encrypted into several thousand different formats. This makes it much more difficult for an attacker to uncover the right format for your system.

    Password Cracking tools
    Note that the use of one-way hashes for passwords does not prevent password crackers from guessing passwords. A password cracker runs a plain-text string through the same one-way hash algorithm used by the system to generate a hash, then compares that generated has with the one stored on the system. If they match, the password cracker has guessed your password.

    This is very much the same process used to authenticate you to a system via a password. When you type your username and password, the system hashes the password you typed and compares that generated hash against the one stored on the system – if they match, you are authenticated.

    Pre-Computed password tables exists today and they allow you to crack passwords on Lan Manager (LM) within a VERY short period of time through the use of Rainbow Tables. A Rainbow Table is a precomputed table for reversing cryptographic hash functions, usually for cracking password hashes. Tables are usually used in recovering a plaintext password up to a certain length consisting of a limited set of characters. It is a practical example of a space/time trade-off also called a Time-Memory trade off, using more computer processing time at the cost of less storage when calculating a hash on every attempt, or less processing time and more storage when compared to a simple lookup table with one entry per hash. Use of a key derivation function that employs a salt makes this attack unfeasible.

    You may want to review “Rainbow Tables” at the links:
    http://en.wikipedia.org/wiki/Rainbow_table
    http://www.antsight.com/zsl/rainbowcrack/

    Today’s password crackers:
    Meet oclHashcat. They are GPGPU-based multi-hash cracker using a brute-force attack (implemented as mask attack), combinator attack, dictionary attack, hybrid attack, mask attack, and rule-based attack.

    This GPU cracker is a fusioned version of oclHashcat-plus and oclHashcat-lite, both very well-known suites at that time, but now deprecated. There also existed a now very old oclHashcat GPU cracker that was replaced w/ plus and lite, which – as said – were then merged into oclHashcat 1.00 again.

    This cracker can crack Hashes of NTLM Version 2 up to 8 characters in less than a few hours. It is definitively a game changer. It can try hundreds of billions of tries per seconds on a very large cluster of GPU’s. It supports up to 128 Video Cards at once.

    I am stuck using Password what can I do to better protect myself?
    You could look at safer alternative such as Bcrypt, PBKDF2, and Scrypt.

    bcrypt is a key derivation function for passwords designed by Niels Provos and David Mazières, based on the Blowfish cipher, and presented at USENIX in 1999. Besides incorporating a salt to protect against rainbow table attacks, bcrypt is an adaptive function: over time, the iteration count can be increased to make it slower, so it remains resistant to brute-force search attacks even with increasing computation power.

    In cryptography, scrypt is a password-based key derivation function created by Colin Percival, originally for the Tarsnap online backup service. The algorithm was specifically designed to make it costly to perform large-scale custom hardware attacks by requiring large amounts of memory. In 2012, the scrypt algorithm was published by the IETF as an Internet Draft, intended to become an informational RFC, which has since expired. A simplified version of scrypt is used as a proof-of-work scheme by a number of cryptocurrencies, such as Litecoin and Dogecoin.

    PBKDF2 (Password-Based Key Derivation Function 2) is a key derivation function that is part of RSA Laboratories’ Public-Key Cryptography Standards (PKCS) series, specifically PKCS #5 v2.0, also published as Internet Engineering Task Force’s RFC 2898. It replaces an earlier standard, PBKDF1, which could only produce derived keys up to 160 bits long.

    PBKDF2 applies a pseudorandom function, such as a cryptographic hash, cipher, or HMAC to the input password or passphrase along with a salt value and repeats the process many times to produce a derived key, which can then be used as a cryptographic key in subsequent operations. The added computational work makes password cracking much more difficult, and is known as key stretching. When the standard was written in 2000, the recommended minimum number of iterations was 1000, but the parameter is intended to be increased over time as CPU speeds increase. Having a salt added to the password reduces the ability to use precomputed hashes (rainbow tables) for attacks, and means that multiple passwords have to be tested individually, not all at once. The standard recommends a salt length of at least 64 bits.

    The other answers are incorrect:

    “It prevents an unauthorized person from trying multiple passwords in one logon attempt.” is incorrect because the fact that a password has been hashed does not prevent this type of brute force password guessing attempt.

    “It minimizes the amount of storage required for user passwords” is incorrect because hash algorithms always generate the same number of bits, regardless of the length of the input. Therefore, even short passwords will still result in a longer hash and not minimize storage requirements.

    “It minimizes the amount of processing time used for encrypting passwords” is incorrect because the processing time to encrypt a password would be basically the same required to produce a one-way has of the same password.
    Reference(s) used for this question:
    http://en.wikipedia.org/wiki/PBKDF2
    http://en.wikipedia.org/wiki/Scrypt
    http://en.wikipedia.org/wiki/Bcrypt
    Harris, Shon (2012-10-18). CISSP All-in-One Exam Guide, 6th Edition (p. 195) . McGraw-Hill. Kindle Edition.

  4. Which of the following issues is not addressed by digital signatures?

    • nonrepudiation
    • authentication
    • data integrity
    • denial-of-service
    Explanation:

    A digital signature directly addresses both confidentiality and integrity of the CIA triad. It does not directly address availability, which is what denial-of-service attacks.

    The other answers are not correct because:

    “nonrepudiation” is not correct because a digital signature can provide for nonrepudiation.
    “authentication” is not correct because a digital signature can be used as an authentication mechanism
    “data integrity” is not correct because a digital signature does verify data integrity (as part of nonrepudiation)

    References:
    Official ISC2 Guide page: 227 & 265
    All in One Third Edition page: 648

  5. Which type of algorithm is considered to have the highest strength per bit of key length of any of the asymmetric algorithms?

    • Rivest, Shamir, Adleman (RSA)
    • El Gamal
    • Elliptic Curve Cryptography (ECC)
    • Advanced Encryption Standard (AES)
    Explanation:

    The other answers are not correct because:

    “Rivest, Shamir, Adleman (RSA)” is incorrect because RSA is a “traditional” asymmetric algorithm. While it is reasonably strong, it is not considered to be as strong as ECC based systems.

    “El Gamal” is incorrect because it is also a “traditional” asymmetric algorithm and not considered as strong as ECC based systems.

    “Advanced Encryption Standard (AES)” is incorrect because the question asks specifically about asymmetric algorithms and AES is a symmetric algorithm.

    References:
    Official ISC2 Guide page: 258
    All in One Third Edition page: 638
    The RSA Crypto FAQ: http://www.rsa.com/rsalabs/node.asp?id=2241

  6. How many bits is the effective length of the key of the Data Encryption Standard algorithm?

    • 168
    • 128
    • 56
    • 64
    Explanation:

    The correct answer is “56”. This is actually a bit of a trick question, since the actual key length is 64 bits. However, every eighth bit is ignored because it is used for parity. This makes the “effective length of the key” that the question actually asks for 56 bits.

    The other answers are not correct because:

    168 – This is the number of effective bits in Triple DES (56 times 3).
    128 – Many encryption algorithms use 128 bit key, but not DES. Note that you may see 128 bit encryption referred to as “military strength encryption” because many military systems use key of this length.
    64 – This is the actual length of a DES encryption key, but not the “effective length” of the DES key.

    Reference:
    Official ISC2 Guide page: 238
    All in One Third Edition page: 622

  7. PGP uses which of the following to encrypt data?

    • An asymmetric encryption algorithm
    • A symmetric encryption algorithm
    • A symmetric key distribution system
    • An X.509 digital certificate
    Explanation:

    Notice that the question specifically asks what PGP uses to encrypt For this, PGP uses an symmetric key algorithm. PGP then uses an asymmetric key algorithm to encrypt the session key and then send it securely to the receiver. It is an hybrid system where both types of ciphers are being used for different purposes.

    Whenever a question talks about the bulk of the data to be sent, Symmetric is always best to choice to use because of the inherent speed within Symmetric Ciphers. Asymmetric ciphers are 100 to 1000 times slower than Symmetric Ciphers.

    The other answers are not correct because:

    “An asymmetric encryption algorithm” is incorrect because PGP uses a symmetric algorithm to encrypt data.

    “A symmetric key distribution system” is incorrect because PGP uses an asymmetric algorithm for the distribution of the session keys used for the bulk of the data.

    “An X.509 digital certificate” is incorrect because PGP does not use X.509 digital certificates to encrypt the data, it uses a session key to encrypt the data.

    References:
    Official ISC2 Guide page: 275
    All in One Third Edition page: 664 – 665

  8. A public key algorithm that does both encryption and digital signature is which of the following?

    • RSA
    • DES
    • IDEA
    • Diffie-Hellman
    Explanation:

    RSA can be used for encryption, key exchange, and digital signatures.
    Key Exchange versus key Agreement

    KEY EXCHANGE
    Key exchange (also known as “key establishment”) is any method in cryptography by which cryptographic keys are exchanged between users, allowing use of a cryptographic algorithm.

    If sender and receiver wish to exchange encrypted messages, each must be equipped to encrypt messages to be sent and decrypt messages received. The nature of the equipping they require depends on the encryption technique they might use. If they use a code, both will require a copy of the same codebook. If they use a cipher, they will need appropriate keys. If the cipher is a symmetric key cipher, both will need a copy of the same key. If an asymmetric key cipher with the public/private key property, both will need the other’s public key.

    KEY AGREEMENT
    Diffie-Hellman is a key agreement algorithm used by two parties to agree on a shared secret. The Diffie Hellman (DH) key agreement algorithm describes a means for two parties to agree upon a shared secret over a public network in such a way that the secret will be unavailable to eavesdroppers. The DH algorithm converts the shared secret into an arbitrary amount of keying material. The resulting keying material is used as a symmetric encryption key.

    The other answers are not correct because:
    DES and IDEA are both symmetric algorithms.
    Diffie-Hellman is a common asymmetric algorithm, but is used only for key agreement. It is not typically used for data encryption and does not have digital signature capability.

    References:
    http://tools.ietf.org/html/rfc2631
    For Diffie-Hellman information: http://www.netip.com/articles/keith/diffie-helman.htm

  9. Brute force attacks against encryption keys have increased in potency because of increased computing power. Which of the following is often considered a good protection against the brute force cryptography attack?

    • The use of good key generators.
    • The use of session keys.
    • Nothing can defend you against a brute force crypto key attack.
    • Algorithms that are immune to brute force key attacks.
    Explanation:

    If we assume a crytpo-system with a large key (and therefore a large key space) a brute force attack will likely take a good deal of time – anywhere from several hours to several years depending on a number of variables. If you use a session key for each message you encrypt, then the brute force attack provides the attacker with only the key for that one message. So, if you are encrypting 10 messages a day, each with a different session key, but it takes me a month to break each session key then I am fighting a loosing battle.

    The other answers are not correct because:
    “The use of good key generators” is not correct because a brute force key attack will eventually run through all possible combinations of key. Therefore, any key will eventually be broken in this manner given enough time.

    “Nothing can defend you against a brute force crypto key attack” is incorrect, and not the best answer listed. While it is technically true that any key will eventually be broken by a brute force attack, the question remains “how long will it take?”. In other words, if you encrypt something today but I can’t read it for 10,000 years, will you still care? If the key is changed every session does it matter if it can be broken after the session has ended? Of the answers listed here, session keys are “often considered a good protection against the brute force cryptography attack” as the question asks.

    “Algorithms that are immune to brute force key attacks” is incorrect because there currently are no such algorithms.

    References:
    Official ISC2 Guide page: 259
    All in One Third Edition page: 623

  10. The Data Encryption Standard (DES) encryption algorithm has which of the following characteristics?
    • 64 bits of data input results in 56 bits of encrypted output
    • 128 bit key with 8 bits used for parity
    • 64 bit blocks with a 64 bit total key length
    • 56 bits of data input results in 56 bits of encrypted output
    Explanation:

    DES works with 64 bit blocks of text using a 64 bit key (with 8 bits used for parity, so the effective key length is 56 bits).

    Some people are getting the Key Size and the Block Size mixed up. The block size is usually a specific length. For example DES uses block size of 64 bits which results in 64 bits of encrypted data for each block. AES uses a block size of 128 bits, the block size on AES can only be 128 as per the published standard FIPS-197.

    A DES key consists of 64 binary digits (“0″s or “1”s) of which 56 bits are randomly generated and used directly by the algorithm. The other 8 bits, which are not used by the algorithm, may be used for error detection. The 8 error detecting bits are set to make the parity of each 8-bit byte of the key odd, i.e., there is an odd number of “1”s in each 8-bit byte1. Authorized users of encrypted computer data must have the key that was used to encipher the data in order to decrypt it.

    IN CONTRAST WITH AES
    The input and output for the AES algorithm each consist of sequences of 128 bits (digits with values of 0 or 1). These sequences will sometimes be referred to as blocks and the number of bits they contain will be referred to as their length. The Cipher Key for the AES algorithm is a sequence of 128, 192 or 256 bits. Other input, output and Cipher Key lengths are not permitted by this standard.

    The Advanced Encryption Standard (AES) specifies the Rijndael algorithm, a symmetric block cipher that can process data blocks of 128 bits, using cipher keys with lengths of 128, 192, and 256 bits. Rijndael was designed to handle additional block sizes and key lengths, however they are not adopted in the AES standard.

    The AES algorithm may be used with the three different key lengths indicated above, and therefore these different “flavors” may be referred to as “AES-128”, “AES-192”, and “AES-256”.

    The other answers are not correct because:
    “64 bits of data input results in 56 bits of encrypted output” is incorrect because while DES does work with 64 bit block input, it results in 64 bit blocks of encrypted output.

    “128 bit key with 8 bits used for parity” is incorrect because DES does not ever use a 128 bit key.

    “56 bits of data input results in 56 bits of encrypted output” is incorrect because DES always works with 64 bit blocks of input/output, not 56 bits.

    Reference(s) used for this question:
    Official ISC2 Guide to the CISSP CBK, Second Edition, page: 336-343
    http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
    http://csrc.nist.gov/publications/fips/fips46-3/fips46-3.pdf

  11. In a known plaintext attack, the cryptanalyst has knowledge of which of the following?

    • the ciphertext and the key
    • the plaintext and the secret key
    • both the plaintext and the associated ciphertext of several messages
    • the plaintext and the algorithm
    Explanation:
    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.

  12. What is the primary role of cross certification?

    • Creating trust between different PKIs
    • Build an overall PKI hierarchy
    • set up direct trust to a second root CA
    • Prevent the nullification of user certificates by CA certificate revocation
    Explanation:

    More and more organizations are setting up their own internal PKIs. When these independent PKIs need to interconnect to allow for secure communication to take place (either between departments or different companies), there must be a way for the two root CAs to trust each other.

    These two CAs do not have a CA above them they can both trust, so they must carry out cross certification. A cross certification is the process undertaken by CAs to establish a trust relationship in which they rely upon each other’s digital certificates and public keys as if they had issued them themselves.

    When this is set up, a CA for one company can validate digital certificates from the other company and vice versa.

    Reference(s) used for this question:

    For more information and illustration on Cross certification: http://www.microsoft.com/technet/prodtechnol/windowsserver2003/technologies/security/ws03qswp.mspx http://www.entrust.com/resources/pdf/cross_certification.pdf

    also see:
    Shon Harris, CISSP All in one book, 4th Edition, Page 727
    and
    RFC 2459: Internet X.509 Public Key Infrastructure Certificate and CRL Profile; FORD, Warwick & BAUM, Michael S., Secure Electronic Commerce: Building the Infrastructure for Digital Signatures and Encryption (2nd Edition), 2000, Prentice Hall PTR, Page 254.

  13. What kind of encryption is realized in the S/MIME-standard?

    • Asymmetric encryption scheme
    • Password based encryption scheme
    • Public key based, hybrid encryption scheme
    • Elliptic curve based encryption
    Explanation:

    S/MIME (for Secure MIME, or Secure Multipurpose Mail Extension) is a security process used for e-mail exchanges that makes it possible to guarantee the confidentiality and non-repudiation of electronic messages.
    S/MIME is based on the MIME standard, the goal of which is to let users attach files other than ASCII text files to electronic messages. The MIME standard therefore makes it possible to attach all types of files to e-mails.

    S/MIME was originally developed by the company RSA Data Security. Ratified in July 1999 by the IETF, S/MIME has become a standard, whose specifications are contained in RFCs 2630 to 2633.
    How S/MIME works

    The S/MIME standard is based on the principle of public-key encryption. S/MIME therefore makes it possible to encrypt the content of messages but does not encrypt the communication.

    The various sections of an electronic message, encoded according to the MIME standard, are each encrypted using a session key.

    The session key is inserted in each section’s header, and is encrypted using the recipient’s public key. Only the recipient can open the message’s body, using his private key, which guarantees the confidentiality and integrity of the received message.

    In addition, the message’s signature is encrypted with the sender’s private key. Anyone intercepting the communication can read the content of the message’s signature, but this ensures the recipient of the sender’s identity, since only the sender is capable of encrypting a message (with his private key) that can be decrypted with his public key.

    Reference(s) used for this question:
    http://en.kioskea.net/contents/139-cryptography-s-mime
    RFC 2630: Cryptographic Message Syntax;
    OPPLIGER, Rolf, Secure Messaging with PGP and S/MIME, 2000, Artech House;
    HARRIS, Shon, All-In-One CISSP Certification Exam Guide, 2001, McGraw-Hill/Osborne, page 570;
    SMITH, Richard E., Internet Cryptography, 1997, Addison-Wesley Pub Co.

  14. What is NOT true with pre shared key authentication within IKE / IPsec protocol?

    • Pre shared key authentication is normally based on simple passwords
    • Needs a Public Key Infrastructure (PKI) to work
    • IKE is used to setup Security Associations
    • IKE builds upon the Oakley protocol and the ISAKMP protocol.
    Explanation:

    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 which are either pre-shared or distributed using DNS (preferably with DNSSEC) and a Diffie–Hellman key exchange to set up a shared session secret from which cryptographic keys are derived.

    Internet Key Exchange (IKE) Internet key exchange allows communicating partners to prove their identity to each other and establish a secure communication channel, and is applied as an authentication component of IPSec.

    IKE uses two phases:

    Phase 1: In this phase, the partners authenticate with each other, using one of the following:
    Shared Secret: A key that is exchanged by humans via telephone, fax, encrypted e-mail, etc.
    Public Key Encryption: Digital certificates are exchanged.
    Revised mode of Public Key Encryption: To reduce the overhead of public key encryption, a nonce (a Cryptographic function that refers to a number or bit string used only once, in security engineering) is encrypted with the communicating partner’s public key, and the peer’s identity is encrypted with symmetric encryption using the nonce as the key. Next, IKE establishes a temporary security association and secure tunnel to protect the rest of the key exchange. Phase 2: The peers’ security associations are established, using the secure tunnel and temporary SA created at the end of phase 1.

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

    Hernandez CISSP, Steven (2012-12-21). Official (ISC)2 Guide to the CISSP CBK, Third Edition ((ISC)2 Press) (Kindle Locations 7032-7048). Auerbach Publications. Kindle Edition.
    and
    RFC 2409 at http://tools.ietf.org/html/rfc2409
    and
    http://en.wikipedia.org/wiki/Internet_Key_Exchange

  15. In a hierarchical PKI the highest CA is regularly called Root CA, it is also referred to by which one of the following term?

    • Subordinate CA
    • Top Level CA
    • Big CA
    • Master CA
    Explanation:

    Reference: Arsenault, Turner, Internet X.509 Public Key Infrastructure: Roadmap, Chapter “Terminology”.

    Also note that sometimes other terms such as Certification Authority Anchor (CAA) might be used within some government organization, Top level CA is another common term to indicate the top level CA, Top Level Anchor could also be used.

  16. What attribute is included in a X.509-certificate?

    • Distinguished name of the subject
    • Telephone number of the department
    • secret key of the issuing CA
    • the key pair of the certificate holder
    Explanation:
    RFC 2459 : Internet X.509 Public Key Infrastructure Certificate and CRL Profile; GUTMANN, P., X.509 style guide; SMITH, Richard E., Internet Cryptography, 1997, Addison-Wesley Pub Co.

  17. What is the primary role of smartcards in a PKI?

    • Transparent renewal of user keys
    • Easy distribution of the certificates between the users
    • Fast hardware encryption of the raw data
    • Tamper resistant, mobile storage and application of private keys of the users
    Explanation:

    Reference: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, 2001, McGraw-Hill/Osborne, page 139;

    SNYDER, J., What is a SMART CARD?.
    Wikipedia has a nice definition at: http://en.wikipedia.org/wiki/Tamper_resistance
    Security

    Tamper-resistant microprocessors are used to store and process private or sensitive information, such as private keys or electronic money credit. To prevent an attacker from retrieving or modifying the information, the chips are designed so that the information is not accessible through external means and can be accessed only by the embedded software, which should contain the appropriate security measures.

    Examples of tamper-resistant chips include all secure cryptoprocessors, such as the IBM 4758 and chips used in smartcards, as well as the Clipper chip.

    It has been argued that it is very difficult to make simple electronic devices secure against tampering, because numerous attacks are possible, including:

    physical attack of various forms (microprobing, drills, files, solvents, etc.)
    freezing the device
    applying out-of-spec voltages or power surges
    applying unusual clock signals
    inducing software errors using radiation
    measuring the precise time and power requirements of certain operations (see power analysis)

    Tamper-resistant chips may be designed to zeroise their sensitive data (especially cryptographic keys) if they detect penetration of their security encapsulation or out-of-specification environmental parameters. A chip may even be rated for “cold zeroisation”, the ability to zeroise itself even after its power supply has been crippled.
    Nevertheless, the fact that an attacker may have the device in his possession for as long as he likes, and perhaps obtain numerous other samples for testing and practice, means that it is practically impossible to totally eliminate tampering by a sufficiently motivated opponent. Because of this, one of the most important elements in protecting a system is overall system design. In particular, tamper-resistant systems should “fail gracefully” by ensuring that compromise of one device does not compromise the entire system. In this manner, the attacker can be practically restricted to attacks that cost less than the expected return from compromising a single device (plus, perhaps, a little more for kudos). Since the most sophisticated attacks have been estimated to cost several hundred thousand dollars to carry out, carefully designed systems may be invulnerable in practice.

  18. What is the main problem of the renewal of a root CA certificate?

    • It requires key recovery of all end user keys
    • It requires the authentic distribution of the new root CA certificate to all PKI participants
    • It requires the collection of the old root CA certificates from all the users
    • It requires issuance of the new root CA certificate
    Explanation:

    The main task here is the authentic distribution of the new root CA certificate as new trust anchor to all the PKI participants (e.g. the users).

    In some of the rollover-scenarios there is no automatic way, often explicit assignment of trust from each user is needed, which could be very costly.

    Other methods make use of the old root CA certificate for automatic trust establishment (see PKIX-reference), but these solutions works only well for scenarios with currently valid root CA certificates (and not for emergency cases e.g. compromise of the current root CA certificate).

    The rollover of the root CA certificate is a specific and delicate problem and therefore are often ignored during PKI deployment.

    Reference: Camphausen, I.; Petersen, H.; Stark, C.: Konzepte zum Root CA Zertifikatswechsel, conference Enterprise Security 2002, March 26-27, 2002, Paderborn; RFC 2459 : Internet X.509 Public Key Infrastructure Certificate and CRL Profile.

  19. Virus scanning and content inspection of SMIME encrypted e-mail without doing any further processing is:

    • Not possible
    • Only possible with key recovery scheme of all user keys
    • It is possible only if X509 Version 3 certificates are used
    • It is possible only by “brute force” decryption
    Explanation:

    Content security measures presumes that the content is available in cleartext on the central mail server.

    Encrypted emails have to be decrypted before it can be filtered (e.g. to detect viruses), so you need the decryption key on the central “crypto mail server”.

    There are several ways for such key management, e.g. by message or key recovery methods. However, that would certainly require further processing in order to achieve such goal.

  20. The RSA Algorithm uses which mathematical concept as the basis of its encryption?

    • Geometry
    • 16-round ciphers
    • PI (3.14159…)
    • Two large prime numbers
    Explanation:

    Source: TIPTON, et. al, Official (ISC)2 Guide to the CISSP CBK, 2007 edition, page 254.

    And from the RSA web site, http://www.rsa.com/rsalabs/node.asp?id=2214 :
    The RSA cryptosystem is a public-key cryptosystem that offers both encryption and digital signatures (authentication). Ronald Rivest, Adi Shamir, and Leonard Adleman developed the RSA system in 1977 [RSA78]; RSA stands for the first letter in each of its inventors’ last names.

    The RSA algorithm works as follows: take two large primes, p and q, and compute their product n = pq; n is called the modulus. Choose a number, e, less than n and relatively prime to (p-1)(q-1), which means e and (p-1)(q-1) have no common factors except 1. Find another number d such that (ed – 1) is divisible by (p-1)(q-1). The values e and d are called the public and private exponents, respectively. The public key is the pair (n, e); the private key is (n, d). The factors p and q may be destroyed or kept with the private key.

    It is currently difficult to obtain the private key d from the public key (n, e). However if one could factor n into p and q, then one could obtain the private key d. Thus the security of the RSA system is based on the assumption that factoring is difficult. The discovery of an easy method of factoring would “break” RSA (see Question 3.1.3 and Question 2.3.3).

    Here is how the RSA system can be used for encryption and digital signatures (in practice, the actual use is slightly different; see Questions 3.1.7 and 3.1.8):
    Encryption

    Suppose Alice wants to send a message m to Bob. Alice creates the ciphertext c by exponentiating: c = me mod n, where e and n are Bob’s public key. She sends c to Bob. To decrypt, Bob also exponentiates: m = cd mod n; the relationship between e and d ensures that Bob correctly recovers m. Since only Bob knows d, only Bob can decrypt this message.

    Digital Signature
    Suppose Alice wants to send a message m to Bob in such a way that Bob is assured the message is both authentic, has not been tampered with, and from Alice. Alice creates a digital signature s by exponentiating: s = md mod n, where d and n are Alice’s private key. She sends m and s to Bob. To verify the signature, Bob exponentiates and checks that the message m is recovered: m = se mod n, where e and n are Alice’s public key.

    Thus encryption and authentication take place without any sharing of private keys: each person uses only another’s public key or their own private key. Anyone can send an encrypted message or verify a signed message, but only someone in possession of the correct private key can decrypt or sign a message.

Subscribe
Notify of
guest
0 Comments
Newest
Oldest Most Voted
Inline Feedbacks
View all comments