Computer ForensicsMidtermExam Name____________________________________ Answer the following questions.you can make your own assumptions. 1.Data acquisition – Study theacquisition methods used by...

1. Determining the Best Acquisition Method
Bit-stream disk-to-image file
It is the most common method and can make more than one copy of the original hard drive. It is used in case of bit by bit replication. Prodiscover, EnCase and FTK
Bit-stream disk-to-disk
It is used when to disk-to-image copy is impossible. Encase is the preferred tool here.
Logical acquisition or sparse acquisition
This method is used when the time is extremely limited or only specific files of interest are to be recovered. Besides these, when fragments of unallocated data needs  to be recovered.
a. Cryptology is a technique which converts a sequence of data into randomly arranged sequence of bits. These are crypted bits but internally they consist of meaningful and hidden information. But to an observer it seems to be meaningless.  It can also be said that it is a study of varied methods of transmitting information in a secured manner so that except the intended receiver no other intruder read the message by removing the disguise. In itself, it both a science and art. Science because it involves a scientific approach and art as there is no one particular way of crypting the data.  Hence people can come up with various methods of their own unique and creative way. In cryptology, the message is converted in to a random order using a “code”. Every character is replaced by another character or by “Cipher/Cipher” where the whole message is converted rather than converting each character.
Cryptanalysis is the method of cracking or breaking opens the encrypted message so as to reveal the hidden information. It is done by getting the decrypting key. It comes under the head of cryptology.
Cryptographic systems have been classified under three headings:
a. Phenomenon of converting plaintext into cipher text - Under this all the encryption algorithms is based on two rules: Substitution and transportation. Substitution is a method of substituting an element with another element. Transportation is the method of rearranging the elements.  All is done with one thing in mind that no information is lost during these processes. Data should be present in disguised form perfectly. 2. Methodology for different types of keys used.
In this method different keys such as secret key, public key, digital signature and hash function are used.
A) Secret key (Symmetric): A single key is used to perform encryption on plain text. Then both the key and plaintext documents are sent to the receiver where it uses the same key so as to decrypt the information. Since both the receiver and sender use same key. It is generally termed as symmetric encryption.
b) Public key- Under this mechanism, the sender and receiver are engaged in an insecure communication but don’t share the secret key.
c) Digital signature - Here the sender signs the sending document and encrypts it with the private key and then sends it to the receiver.
d) Hash Function: The hash functions which is one of the most popular in recent times particularly in Internet Security protocols is a one way of encryption that represents small sized bits which are generated from large sized file. Generating hash codes are generally faster than other methods which make it more popular for authentication and integrity.
3. Methodology for processing plain text. Under this cipher block processes the input block of data. This phenomenon uses substitution cipher process. It is an algorithm which uses symmetric key algorithm.
In this method an output block for each input block of elements are processed by a block cipher. This proposed algorithm uses a substitution cipher method and is a symmetric key algorithm using the technique of stream cipher.
Steganography similar to cryptography is also a method of concealing secret messages in a document. The origin of the word steganography comes from the Greek word called “Steganos” which means “covered/secret’. Hence, steganography implies ‘secret writing” Steganography essentially...