Question: There are three main types of cryptographic algorithms: (1) secret key

Question

Question: There are three main types of cryptographic algorithms: (1) secret key, (2) public key, and (3) hash functions. Pick an algorithm for any one of these types (e.g., DES, AES, RSA, MD5) and describe how it works and where it is applied (For example SSL uses 3DES or DES) for message encryption. Use your own words. When you pick an algorithm, try not to repeat. Be sure to reference your sources.

Answer: Hash functions involves encrypting passwords. It takes the data and creates a hash out of it, which is a string of data with 3 important properties: 1. the same data will always produce the same hash 2. you can't reverse it back to the original data 3. you can't create another string of data that will create the same hash Also, hash sizes of 128 bits are sufficient for most applications. For security systems tho, you might want to consider 168 to 256 bits as many hash functions are currently being revised. Hashing's most important use is protecting passwords. If the system stores a password hash instead of a password, it can check an incoming password by hashing it and seeing if the hashes match. It's not possible to use the hash to authenticate. The system increases its security by only knowing the password in the brief moments it needs to when changing it or verifying it. You can find hashtags in a lot of today's social networks such as: Twitter, Facebook, Google+, Instagram, and Pinterest. Most hashing algorithms descend from the MD4 family. MD4 is an earlier version of MD5. It's used to verify data integrity through the creation of a 128-bit message digest from data input that is claimed to be as unique to that specific data as a fingerprint is to the specific individual. "The MD4 hashing algorithm was developed by Ronald Rivest specifically to allow very easy software implementation. The MD4 algorithm and subsequent SHA algorithms use 32 bit variables with bitwise Boolean functions such as the logical AND, OR, and XOR operators to work through from the input to the output of hash." (Behrens, 2014)

Explanation / Answer

Answer:-

AES (Advanced Encryption Standard) is a symmetric encryption algorithm - one key can be used to encode, and then decrypt the message. It is found at least six times quicker than triple DES .We need to firmly share that key with the system as we are exchanging encrypted data with, otherwise other people can decrypt our data, or pretend to create encrypted data on our behalf.

Feature of AES:-

Software implementable in C and Java

Stronger and faster than Triple-DES

Symmetric key symmetric block cipher

Encryption Process:-

               At this point, we limit to description of a typical round of AES encryption. Each round contain of four sub-processes. The first round process is shown below:

1) Byte Substitution (Sub Bytes):

               The 16 input bytes are replaced by looking up a fixed table (S-box) specified in design. The outcome is in a matrix of four rows and four columns.

2) Shift rows:

              Each of the four rows of the matrix is shifted to the left. Any entries that ‘fall off’ are re-inserted on the right side of row. Shift is carried out as follows:

First row is not shifted.

Second row is shifted one (byte) position to the left.

Third row is shifted two positions to the left side

Fourth row is shifted three positions to the left side.

Hence the result is a new matrix consisting of the same 16 bytes but shifted with respect to each other.

(3)Mix Columns:

                                Each column of four bytes is now converted using a special accurate task. This task takes as input the four bytes of one column and outputs four completely new bytes, which replace the original column. The outcome is another new matrix consisting of 16 new bytes. This step should not be performed in the last round.

(4)Add round key:

          The 16 bytes of the matrix are now measured as 128 bits and are XORed to the 128 bits of the round key. If this is the last round then the output is the cipher text. Then, the resultant 128 bits are interpreted as 16 bytes and we create another similar round.

Decryption Process:-

                            The process of decryption of an AES ciphertext is similar to the encryption process in the reverse order. Each round consists of the four courses directed in the reverse order:

1)Add round key

2)Mix columns

3)Shift rows

4)Byte substitution

                       Since sub-processes in each round are in reverse manner, unlike for a Feistel Cipher, the encryption and decryption algorithm needs to be separately implemented, although they are very closely related.

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