Goals of cryptography

cryptography concepts

cryptographic mathematics

password

modern cryptography

Symmetric cipher

Password life cycle

Understand the role confidentiality, integrity, and non-repudiation play in cryptographic systems. Secrecy is one of the main goals pursued by cryptography. This goal protects the confidentiality of data at rest and in transit. Integrity assures the message recipient that the data has not been altered (either intentionally or unintentionally) from the time it was created to the time it was accessed. Non-repudiation provides irrefutable proof. The sender of the message did authorize the message. This prevents the sender from later denying that he sent the original message.

Understand the ways in which cryptographic systems achieve authentication goals. Identity authentication can provide user identity protection. Challenge-response protocols are one possibility for performing authentication, requiring the remote user to encrypt a message with a key known only to the communicating parties. Both symmetric and asymmetric cryptosystems can perform authentication.

Familiar with basic cryptography terminology. For a sender to send a private message to a recipient, he first extracts the plaintext (unencrypted) message and then encrypts it using an algorithm and a key. This will generate a ciphertext message for delivery to the recipient. The recipient will then use the same algorithm and key to decrypt the ciphertext and reconstruct the original plaintext message for viewing.

Understand the difference between codes and passwords and explain the basic types of passwords. A code is a cryptographic system of symbols acting on words or phrases that is sometimes confidential but does not always provide confidentiality security services. A password will always hide the true meaning of the message. Understand how the following types of ciphers work: shift ciphers, substitution ciphers (including one-time pads), stream ciphers, and block ciphers.

Understand the requirements for successfully using a one-time pad. For a one-time pad to be successful, the key must be generated randomly and without using any known pattern. The key must be at least as long as the message being encrypted, the pad must be protected from physical leakage, and each pad must be discarded after being used once.

Learn about segmentation. Splitting knowledge means splitting the information or permissions required to perform an operation among multiple users to ensure that no one person has enough permissions to compromise the security of the environment. N only replacing M control is an example of segmented knowledge.

Understanding the Cost Function (Cost Factor) The cost function or cost factor measures the strength of a cryptographic system by measuring the effort required to decrypt a message in terms of cost and/or time. The time and effort required to fully implement a brute force attack on an encryption system is usually expressed by the cost function evaluation. The protection provided by a cryptographic system is directly proportional to the value of its cost function/factor.

Understand the importance of key security. Cryptographic keys provide the necessary element of confidentiality for a cryptographic system. Modern cryptographic systems provide adequate security with keys that are at least 128 bits long.

Learn the differences between symmetric and asymmetric cryptosystems. Symmetric key cryptosystems (or secret key cryptosystems) rely on the use of an exclusive secret key. Symmetric key cryptosystems operate much faster than asymmetric cryptosystems, but they do not support scalability, easy distribution of keys, and non-repudiation. Asymmetric cryptosystems use public-private key pairs for communication between two parties, but operate much slower than symmetric algorithms.

Be able to explain the basic operating modes of symmetric cryptosystems. Symmetric cryptosystems operate in several discrete modes: Electronic Code Book (ECB) mode, Cipher Block Chaining (CBC) mode, Cipher Feedback (CFB) mode, Output Feedback (OFB) mode, Counter (CTR) mode, Galois/Counter mode (GCM) and Counter Mode (CCM) with Cipher Block Chained Message Verification Code. ECB mode is considered the least secure and is only used to transmit short messages. 3DES uses two or three different keys to iterate DES three times to increase the effective key strength to 112 or 168 bits respectively.

Learn about Advanced Encryption Standard (AES). The Advanced Encryption Standard (AES) uses the Rijndael algorithm and is a U.S. government standard for securely exchanging sensitive, unclassified data. AES uses 128, 192, and 256-bit key lengths and a fixed block size of 128 bits to achieve a level of security that is far superior to the older DES algorithm.

Ryan manages the cryptographic keys used by his organization at his expense. Here's how he should select and manage these Rachels #达中Which ones are correct? (Check all that apply.) A. If data is expected to remain secret, the key should be long enough to withstand future attacks. B. Keys should be chosen that can be generated through some predictable pattern. C. The key should remain non-deterministic. D. The longer the key, the greater the security strength it can provide.

You are developing a security product that must facilitate the exchange of symmetric encryption keys between two parties who cannot securely exchange keys face-to-face. Which algorithm might you use? A. Rijndael B. Blowfish C. Vernam D. Diffic-Hellman

What comes into play when the relationship between the plaintext and the key is complex enough that an attacker cannot determine the key simply by continually modifying the plaintext and analyzing the ciphertext? (Select all that apply.) A. Confusion B. Displacement C. Polymorphism D. Diffusion

Randy is implementing an AES-based cryptographic system for internal use within his organization; he would like to learn more about how he can use this cryptographic system to achieve his goals. Which of the following daily targets can be achieved by AES? (Answers that are more useful than all roads.) A. Non-repudiation B. Confidentiality C. Identity authentication D.Integrity

Brian discovered encrypted data left behind by attackers when communicating with each other on one of his systems. He tried using various encryption techniques to decrypt the data, but failed. he thinks. The data may be protected using an unbreakable system. So, only which cryptosystem, if executed properly, can be considered unbreakable? A. Shift code B. Replace password C. Commercial Grade Encryption Standard (AES) D. Single copy

Helen plans to use one-time pads to meet her organization's unique encryption needs. She attempts to determine the requirements for using such a cryptographic system. So, which of the following are requirements for using a one-time pad? (Check all that apply.) The length of the A encryption key must be at least half the length of the message to be encrypted. B Encryption keys must be randomly generated. C. Each single-time pad must be used only once. D. The one-time pad must be protected from leakage under physical protection.

Brim manages a symmetric cryptosystem used by 20 users, where each user can communicate privately with any other user. One user has lost control of his account. Brian believes that this user's keys have been compromised. How many keys must she replace? A.1 piece B. 2 C. 19 D. 190

Dave is developing a key escrow system that requires multiple people to be present together to quickly complete a transaction, but does not require all participants to be present. What technology is Dave using? A. Split knowledge B.N takes M control C.Cost function D. Zero-knowledge proof

Which of the following is used to increase cryptographic strength by encrypting the same message with the same key each time, creating a unique ciphertext each time? A. Initialization vector B. Vigenere Password C steganography D. Stream cipher

Tammy is selecting an operating mode for a symmetric cryptosystem she will use at her workplace. She hopes that the model she sends can not only provide confidentiality protection for the data, but also ensure the authenticity of the data. Which of the following models would meet her requirements? A.ECB B. GCM C. OFB D.CTR

Which of the following encryption algorithm modes would allow the undesirable properties of errors to propagate between blocks? A. Electronic Code Book (ECB) B. Cipher Block Chaining (CBC) C.Output feedback (OFB) D. Counter (CTR)

Victoria was selecting an encryption algorithm for the organization she worked for, and wanted to choose the most secure symmetric algorithm from a list of encryption algorithms supported by a software package she planned to use. If the following algorithms are supported by this package, then is Victoria the best choice? A. AES-256 B. 3DES C.RCA D. Skipjack

The ones institute, which has six employees, uses a symmetric key encryption system to ensure the confidentiality of communications. If all employees need to communicate privately with all other employees, how many keys will they need? A.1 piece B. 6 C. 15 D. 30 pieces