Describe the different categories of symmetric encryption algorithms. Outline th

Question

Describe the different categories of symmetric encryption algorithms. Outline the symmetric encryption process and explain the components involved in the process. What is cryptanalysis? Give an example of a cryptanalytic problem. Describe how a simple substitution cipher works, like the Caesar cipher. Describe the components of a digital stream cipher. Why do modern security systems avoid using RC4? What is the difference between a stream cipher and a one-time pad? Explain the relationship between modular arithmetic and the Caesar cipher. How do data errors in ciphertext encrypted with a stream cipher affect the decrypted plaintext? Summarize the different situations in which people use file encryption software. Compare the behavior of built-in Windows file encryption with using a separate encryption application program. Describe the steps performed when a file encryption program encrypts file. Describe the steps performed when a file encryption program decrypts a file. Why should a file encryption program overwrite the plaintext in a file after the file has been encrypted? Summarize basic considerations for secure, trustworthy software. Summarize the basic security features of a well-written file encryption program.

Explanation / Answer

R1)Answer:

Some examples of popular symmetric algorithms (symmetric-key algorithms):
AES/Rijndael
Blowfish
CAST5
DES
IDEA
RC2
RC4
RC6
Serpent
Triple DES
Twofish

AES:

The Advanced Encryption Standard (AES) is a symmetric-key block cipher algorithm and U.S. government standard for secure and classified data encryption and decryption.

In December 2001, the National Institute of Standards (NIST) approved the AES as Federal Information Processing Standards Publication (FIPS PUB) 197, which specifies application of the Rijndael algorithm to all sensitive classified data.

The Advanced Encryption Standard was originally known as Rijndael.

Advanced Encryption Standard, a symmetric 128-bitblock data encryption technique developed by Belgian cryptographers Joan Daemen and Vincent Rijmen. The U.S government adopted the algorithm as its encryption technique in October 2000, replacing the DES encryption it used. AES works at multiple network layers simultaneously. The National Institute of Standards and Technology (NIST) of the U.S. Department of Commerce selected the algorithm, called Rijndael (pronounced Rhine Dahl or Rain Doll), out of a group of five algorithms under consideration, including one called MARS from a large research team at IBM.

While the terms AES and Rijndael are used interchangeably, there are some differences between the two. AES has a fixed block size of 128-bits and a key size of 128, 192, or 256-bits, whereas Rijndael can be specified with any key and block sizes in a multiple of 32-bits, with a minimum of 128-bits and a maximum of 256-bits.

DES:

The Data Encryption Standard (DES) is an outdated symmetric-key method of data encryption.

DES works by using the same key to encrypt and decrypt a message, so both the sender and the receiver must know and use the same private key. Once the go-to, symmetric-key algorithm for the encryption of electronic data, DES has been superseded by the more secure Advanced Encryption Standard (AES) algorithm.

The data encryption standard (DES) is a common standard for data encryption and a form of secret key cryptography (SKC), which uses only one key for encryption and decryption. Public key cryptography (PKC) uses two keys, i.e., one for encryption and one for decryption.

3DES:

Triple Data Encryption Standard (DES) is a type of computerized cryptography where block cipher algorithms are applied three times to each data block. The key size is increased in Triple DES to ensure additional security through encryption capabilities. Each block contains 64 bits of data. Three keys are referred to as bundle keys with 56 bits per key. There are three keying options in data encryption standards:

R3)Answer:

Cryptanalysis:

Cryptanalysis is the decryption and analysis of codes, ciphers or encrypted text. Cryptanalysis uses mathematical formulas to search for algorithm vulnerabilities and break into cryptography or information security systems.

Cryptanalysis attack types include:

R4)Answer:

substitution cipher:

substitution cipher is a method of cryptography (the science of writing, analyzing, and deciphering codes) which converts standard language or plaintext into coded language or ciphertext, by replacing units of plaintext in accordance with a fixed set of rules. These plaintext units may be individual letters or characters, letter pairs, triplets, or other combinations.

Substitution ciphers may replace only the letters of the standard alphabet with ciphertext, or apply substitutions to spaces and punctuation marks as well.

a substitution cipher is a method of encoding by which units of plaintext are replaced with ciphertext, according to a fixed system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing the inverse substitution.

Substitution ciphers can be compared with transposition ciphers. In a transposition cipher, the units of the plaintext are rearranged in a different and usually quite complex order, but the units themselves are left unchanged. By contrast, in a substitution cipher, the units of the plaintext are retained in the same sequence in the ciphertext, but the units themselves are altered.

R5)Answer:

components of a digital stream cipher:

The components of a stream cipher are key, key stream algorithm, 0101key stream, 1101 Plaintext, 1000 Cipher text.

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