Ch. 7: PKI and Cryptographic Applications

All of the cryptosystems below provide equal protection. Match the cryptosystem with the equivalent key length. 1. RSA 2. DSA 3. Elliptic curve A. 160 bits B. 1,024 bits

1. B 2. B 3. A

rainbow tables

a type of brute force attack tactic. they provide precomputed values for cryptographic hashes

chosen ciphertext -

ability to decrypt chosen portion of the ciphertext message

analytic attack

algebraic manipulation - reduces the complexity of the algorithm's logic.

Known Plaintext

attacker has a copy of the encyrpted message along with the plaintext message used to generate the ciphertext.

Meet in the Middle

attacker uses a known plaintext message. plaintext is encrypted using every possible key (k1) and the equivalent is decrypted using all possible keys (k2).

brute force

attempts every possible valid combination for a key or password.

What can you use to identify the authenticity of certificates and identify revoked certificates?

certificate revocation lists online certificate status protocol

What is the international standard that governs digital certificates? A. X.809 B. X.509 C. the International Governance Agreement for Digital Certificates (IGADC) D. XD.505

B. X 509

What is a Hardware security Module (HSM)?

a hardware device that stores and manages encryption keys in a secure manner.

What is the MD2 Algorithm, and what is its key weakness?

the MD2 hash algorithm was developed by Ronald Rivest in 1989 - to provide secure hash function for 8-bit processors. ** Cryptanalytic attacks against MD2 exist ** - The Checksum is not appended to the message before digest computation, so collisions can occur. It is also not a one-way function. MD2 pads the message so that its length is a multiple of 16 bytes. It then computes a 16-byte checksum and is added to the end of the message. A 128 bit message digest is then generated by using the entire original message along with the appended checksum.

Which key should I use? scenario: 1. Encrypt a message 2. decrypt a message 3. you want to digitally sign a message you're sending to someone else. 4. if you want to verify the signature on a message sent by someone else. A. your private key B. the sender's public key C. the recipient's public key D. your public key

1. C 2. A 3. A 4. B

Matching When sending emails: 1. if you need confidentiality when sending an email message, you must: 2. if you need integrity, you must: 3. if you need authentication, integrity and/or nonrepudiation, you should: 4. if your message requires confidentiality, integrity, authentication and non-repudiation: A. digitally sign the message B. hash the message C. encrypt the message and digitally sign D. encrypt the message

1. D 2. B 3. A 4. C

Alice wants to send a signed message to Bob. Put the steps into chronological order

1. alice generates a message digest using a hashing algorithm, such as SHA-3-512 2. alice encrypts the message digest using her private key [this is now the digital signature] 3. alice appends the signed message digest to the plaintext message. 4. alice sends the appended message to bob then bob must do the following: 1. decrypt the digital signature using Alice's public key 2. use the same hashing function to create a message digest of the full plaintext message received from Alice 3. compare the decrypted message digest he received from alice with message digest he computed himself. if the two digests match, he can be assured that the message was sent by Alice.

What is the purpose/goal of digital signature infrastructures?

1. digitally signed messages assure the recipient that the message truly came from the claimed sender. they enforce nonrepudiation 2. digitally signed messages assure the recipient that the message was not altered while in transit between the sender and recipient. this protects against malicious and unintentional modification.

What are the two encryption techniques used to protect data traveling over networks? (circuit encryption)

1. link encryption - protects the entire communications circuits by creating a secure tunnel between two points. - Usually used by businesses. - Occurs on the lower layers of the OSI model. - all the data - including the header, trailer, address, and routing data - is all encrypted. 2. end to end encryption - protects communications between two parties + is performed independently of link encryption. - SSH is one example of end to end also supports DES, Triple DES, IDEA, and Blowfish - upper layers of OSI model. - faster than link but more vulnerable to eavesdropping

What are the five basic requirements of a cryptographic hash function?

1. the input can be of any length 2. the output has a fixed length 3. the hash function is relatively easy to compute for any input. 4. the hash function is a one-way (meaning that it is extremely hard to determine the input when provided with the output) 5. the hash function is is collision free (it is extremely hard to find two messages that produce the same hash value)

What is required by X.509?

1. version of x.509 to which the certificate conforms to 2. serial number from the certificate creator 3. signature algorithm identifier 4. issuer name (identification of the certificate authority issuing certificate) 5. validity period (dates) 6. subject's name (name of entity that owns the public key contained in the certificate) 7. subject's public key (the most important part of the certificate) Current version - v. 3 - supports certificate extensions (customized variables containing data inserted into the certificate by the certificate authority to support tracking of certificates or various applications.

What is Public Key Infrastructure?

A public key infrastructure (PKI) is a system for the creation, storage, and distribution of digital certificates which are used to verify that a particular public key belongs to a certain entity

How would Alice have ensure confidentiality? (digital signatures fulfill the goals of integrity, authentication, and nonrepudiation, but an extra step must be taken to ensure privacy)

After appending the signed message digest to the plaintext message, Alice could have encrypted the entire message with Bob's public key. Then Bob's first step would be to decrypt the message with his private key.

El Gamal is an algorithm similar to the RSA algorithm, based on the mathematical principles behind the Diffie-Hellman key exchange algorithm. What is the major weakness of El Gamal?

El Gamal doubles the length of any message it encrypts. This presents difficulties when encrypting long messages or data that will be transmitted over a narrow bandwidth communications circuit.

What is Merkle-Hellman Knapsack?

An early asymmetric algorithm. Like RSA, it is based on the difficulty of performing factoring operations, but it relies on a component of set theory known as *super-increasing sets* rather than large prime numbers. INEFFECTIVE - broken in 1984.

Which is not a currently approved standard encryption algorithm by DSS? A. The Digital Signature Algorithm (DSA) B. Rivest-Shamir-Adleman (RSA) algorithm C. Secure Hash Algorithm 3 (SHA 3) D. Elliptive Curve DSA

C. Secure Hash Algorithm is not approved by DSS

what is the purpose of Digital Rights Management (DRM)?

DRM software uses encryption to enforce copyright restrictions on digital media, including music, movies, ebooks, video games, documents. Movie industry uses 2 major technologies to protect mass-distributed media: 1. high-bandwidth digital content protection (HDCP). works over digitally connected movies (incl HDMI, DVI) hackers made this ineffective 2. advanced access content system - protects content on blu ray and HD dvd media. Hackers can attack + retrieve AACS encryption keys and post them on the internet. E-Book: most successful deployment of DRM technology. Adobe offers Adobe Digital Experience Protection Technology (ADEPT) to provide DRM technology for ebooks in a variety of formats.

What is the purpose of digital certificates?

Digital certificates provide communicating parties with the assurance that the people they are communicating with truly are who they claim to be.

What is ISAKMP used for? (Internet Security Association and Key Management Protocol)

ISAKMP provides background security support services for IPsec by negotiating, establishing, modifying, and deleting security associations. ISAKMP manages Security Associations (SAs) ISAKMP's four basic requirements: 1. authenticate communicating peers 2. create and manage security associations 3. provide key generation mechanisms 4. protect against threats (replay and denial of service attacks)

What is MD4?

In 1990, Rivest enhanced his message digest algorithm to support 32-bit processors and increase the level of security. **Not secure, personal computers can be used to find collisions for MD4 message digests in less than a minute** It first pads the message to ensure that the message length is 64 bits smaller than a multiple of 512 bits. Ex: a 16-bit message would be padded with 432 additional bits of data to make it 448 bits, which is 64 bits smaller than a 512 bit message. The MD4 Algorithm then processes 512 bit blocks of the message in three rounds of computation. the final output is 128 bit message digest.

What is the RSA algorithm?

RSA is short for Rivest-Shamir-Adleman algorithm. It is the most commonly used public key encryption algorithm in use today. The RSA algorithm depends on the computational difficulty inherent in factoring large prime numbers.

What is MD5?

MD5, like MD4, also processes 512-bit blocks of message, but it uses four distinct rounds of computation to produce a digest of the same length as the MD2 and MD4 algorithms (128 bits). MD5 has the same padding requirements as MD4. **Not secure: subject to collisions. It is possible to create two digital certificates from different public keys that have the same MD5 hash** MD5 = more security features the **reduce the speed of message digest production significantly**

What are some common secure email standards in use today?

Pretty Good Privacy (1991) and S/MIME. PGP combines the CA hierarchy with the "web of trust" concept- you need to be trusted by a PGP user before using the system. there are two versions of PGP. The commercial version uses RSA for key exchange, ISEA for encryption and decryption, and MD5 for message digest production. the PGP free version uses Diffie-Hellman key exchange, the Carlisle Adams/Stafford Tavares (CAST) 128-bit encryption/decryption algorithm and the SHA-1 hashing function. the S/MIME protocol has emerged as a de facto standard for encrypted email. S/MIME uses the RSA encryption algorithm and is baceked by major industry players. it is used by Microsoft Outlook and Office 365, mozilla thunderbird, mac OSX mail and gsuite. There are some challenges to widespread adoptions (technical limitations)

What is the Elliptic Curve?

Proposed by Neal Koblitz and Victor Miller in 1985. It is based off very complex mathematical concepts, and is more difficult to solve than RSA encryption.

What is the Secure Hash Algorithm?

SHA and SHA-1, SHA-2, and SHA-3, are government standard hash functions promoted by NIST and specified in gov't publications such as the Secure Hash Standard (SHS) and the Federal Information Processing Standard (FIPS) SHA-1 takes an input of virtually any length and produces a 160-bit message digest. The SHA-1 algorithm processes a message in 512 bit blocks. If the message length is not a multiple of 512 bits, SHA-1 pads the message with additional data until the data reaches the next 512 bits. **SHA-3 offers the same variants and hash lengths as SHA-2, using a more secure algorithm** SHA-2 has four variants: 1. SHA 256- 256 bit message digest using a 512 bit block size. 2. SHA 224 - a truncated version of the SHA-256 hash to produce a 224 bit message digest using a 512 bit block size 3. SHA-512 - a 512 bit message digest using a 1,024 bit block size. 4. SHA-384 uses a truncated version of the SHA-512 hash to produce a 384 bit digest using a 1,024 bit block size.

Know all the Hash algorithms and their hash value lengths

SHA-1: 160 SHA-224: 224 SHA 256: 256 SHA 384: 384 SHA 512: 512 MD5 = 128 MD4 = 128 MD2 = 128 HMAC = Variable HAVAL = 128, 160, 192, 224, 256 bits

What is SSL (Secure Sockets Layer)?

SSL provides client/server encryption for web traffic. HTTPS uses port 443 to negotiate encrypted communications sessions between webservers and browser clients. **SSL is the de facto internet standard**

How does SSL work?

SSL relies on the exchange of server digital certificates to negotiate encryption/ decryption parameters between the browser and web server. SSL's goal is to create secure communications channels that remain open for an entire web browsing session. Steps: 1. when a user accesses a website, the browser retrieves the server's public key to encrypt it, and then sends the encrypted symmetric key to the server. 2. browser creates a random symmetric key, uses server's public key to encryp it, then sends encrypted symmetric key to the server. 3. server decrypts the symmetric key using its own private key, and the two systems exchange all future messages using the symmetric encryption key. **efficient - sets ups communications w/ asymmetric cryptography and then uses symmetric key for all other correspondences.

What are four of the most common hashing algorithms?

Secure Hash Algorithm (SHA) Message Digest 2 (MD2) Message Digest 4 (MD4) Message Digest 5 (MD5) also see: Hash message authentication code (HMAC) Hash of Variable Length (HAVAL): a modification of MD5

What are the two technologies reposnsible for encryption and of most web browsers?

Secure Socket Layer (SSL) and Transport Layer Security (TLS)

What is steganography?

Steganography uses cryptographic techniques to embed secret messages within another message. Frequently uses images or WAV files. used by criminals but also for legitimate purposes (such as watermarking intellectual property)

What is the importance of key length?

The longer the key length, the more difficult it is to defeat (longer processing time required to defeat the cryptosystem)

Put the certificate authority process into order. A. verification B. enrollment C. revocation

The order is as follows: Enrollment, Verification, Revocation. In enrollment, you prove your identity. the CA creates an X.509 digital ceritficate containing your identifying infomraiton and a copy of your public key. the CA signs the certificate using the CA's private key, and provides you with a copy of your signed digital certificate. In verification, you verify your certificate by checking the CA's digital signature using the CA's public key. you can also check that the certificate was not revoked (by using the Certificate revocation list or the Online Certificate Status Protocol (OCSP) In revocation, a certificate authority needs to revoke a certificate. this can occur for the following reasons: - certificate compromised - certificate was erronously issued - the details of the certificate has changed - the security association changed

What is TLS?

Transport Layer Security - also called 3.1. effectively the successor to SSL.

T/F Schnorr's signature algorithm and Nyberg Rueppel's signature algorithm are digital signature algorithms

True

T/F NIST specifies the digital signature algorithms acceptable for federal gov't use in FIPS, also known as the Digital Signature Standards (DSS)

True

T/F: Digital signature algorithms rely on a combination of public key cryptography and hashing functions

True

IP Sec is a security architecture that supports secure communications, to set up a secure channel to exchange information between two entities.

Usually used to connect two networks, but can also be used to connect two individual computers. Does not dictate all implementation, but is an open, modular framework that allows manufacturers and software developers to develop IPSec for their own needs. IPSec uses public key cryptography to provide encryption, access control, nonrepudiation, and message authentication using IP based protocols. **widely accepted** IPSec is made of two components: 1. the Authentication Header (AH) provides assurances of message integrity and nonrepudiation. AH also provides authentication and access control and prevents relay attacks. 2. the Encapsulating Security Payload provides confidentiality and integrity of packet contents. it provides encryption and limited authentication and prevents replay attacks.

IPSec provides for two discrete modes of operation. What is the difference between transport mode and tunnel mode?

When IPSec is used in transport mode, only the packet payload is encrypted. This is for peer to peer communication. In Tunnel mode, the entire packet including the header is encrypted. This mode is designed for gateway-to-gateway communication.

What are the two main types of Wireless Networking?

Wired Equivalent Privacy (WEP) and Wifi Protected Access (WAP) You should never use WEP encryption on a wireless network. WPA improves WEP, but it is also not secure. WEP uses TKIP (the Temporal Key Integrity Protocol). You can use WPA2, which adds AES cryptography.

What is IEEE 802.1x?

a common used security standard which provides a flexible framework for authentication and key management in wired and wireless networks. To use 802.1x, client runs a piece of software known as the supplicant. (see page 265 in book for more details).

What is Hash of Variable Length (HAVAL)?

a modification of MD5, it uses 1,024 bit blocks and produces hash values of 128, 160, 192, 224, and 256 bits.

implementation attack

exploits weaknesses in the implementation of a cryptography system. focused on exploiting the software code, not just errors and flaws but the methodology employed to program the encryption system.

frequency analysis and the ciphertext only attack

frequency analysis - counting the number of times each letter appears in the ciphertext. (AEIOU would show up the most)

Know these cryptographic attacks: Analytic attack implementation attack statistical attack brute force (rainbow tables) frequency analysis and the ciphertext only attack known plaintext chosen ciphertext chosen plaintext meet in the middle man in the middle birthday replay

know what all of these do!

Cryptography in Networking includes Circuit Encryption, IPsec, the Internet Security association and Key Management Protocol (ISAKMP), and Wireless Networking

know what these are.

Man in the Middle

malicious individual sits between two communicating parties and intercepts all communications

Birthday attack (also collision or reverse hash matching)

seeks to find flaws in the one-to-one nature of hashing functions. attacker seeks to substitute a digitally signed communication w/ a different message that produces the same message digest, maintaining hte valididty of the original digital signature.

statistical attack

statistical weaknesses in cryptosystem. (like the inability to produce truly random numbers)

What is HMAC? (the Hashed Message Authentication Code)

the HMAC algorithm implements a partial digital signature. it guarantees the integrity of a message during transmission, but it doesn't provide for nonrepudiation.

What is the purpose of registration authorities?

they help certfiicate authorities (like AWS, symantec, godaddy) to verify users' identities prior to issuing digital certificates.

What is the purpose of a hash function?

they take a potentially long message and generate a unique output value derived from the content of the message. 1. the recipient can use the same hash function to recompute the message digest from the full message. if it doesn't match, then they know it's been modified in transit. 2. the message digest can be used to implement a digital signature algorithm.

Salting passwords

this is a way to combat the use of brute force attacks. salts are random values added to the end of a password before the OS hashes the password.

replay

used against cryptographic algorithms that don't incorporate temporal protections. malicious individual intercepts encrypted messages and then later replays the captured message to open a new session. counteract this by using a time stamp + expiration period into each message.