Site Loader

The flow diagram in the Figure 4 explains the systematic operation
of the application. Since the application has more than one task, no task is
depended on other task. Any task can be performed on request of the user. So
the user input determines the task to be executed. Fundamental input parameters
for any module or task in the application are the cover image and the data file
type. An Image file can act as a medium to cover the message. Data file can be
either text or pdf or any other file type. After the valid selection of cover
image and data file and the right encryption key or the password has been
entered, the hiding operation that needs to be performed is decided. Before
hiding, appropriate error message is thrown if the inputs are invalid. If the
all inputs are valid then save window will be opened for user to select the
stego-image destination. Now the data file is encoded on the selected input.
Finally, based on the input, output is drawn. The process used to encode are
discussed later in the chapter.In this application at certain stage data is encrypted upon user
request. AES encryption of

256 bits cipher key size is used to safe guard the cloud user data.
The data is encrypted using the secrete key and IV generated from the password
provided by the user using Salt value. A
salt is random data that is used as an additional input to a one-way function
that “hashes” a password. Salts are closely related to the concept of
nonce. The primary function of salts is to defend against dictionary attacks or
against its hashed equivalent, a pre-computed rainbow table attack 2. Salts are used to safeguard passwords in storage. Historically a
password was stored in plaintext on a system, but over time additional
safeguards developed to protect a user’s password against being read from the
system. A salt is one of those methods 3. To secure the AES symmetric key, we need public key cryptographic
algorithm. So we use RSA encryption algorithm for that purpose. And also to
make our model more secure we use a new 
key for each session to ensure that key isn’t known by attackers.

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4.1.1   
Hashing Algorithm Used

In our model before encryption, we need
to compute the hash code for the secret data using a cryptographic hashing
algorithm to ensure data integrity. Hashing algorithm is a mapping of arbitrary
length messages to n-bit hash code. Due to the enhanced security provided by
the AES depending on its three different key sizes, it is necessary to produce
a companion hash algorithms which provide the same levels of security. In this
paper we use SHA-256 hash function to preserve cloud data integrity. SHA-256
operates as the same manner of MD5 and SHA-1where: First, the message
is padded with its length in such a way that the result is a multiple of 512
bits long. Then, it parsed into 512-bit message blocks M (1); M (2); …;
M (N). The message blocks are processed one at a time beginning with a fixed
initial hash value H (0), and sequentially compute H(i) using the following
equation until H(N) which is the hash  of
M    

4.1.2   
Steganography Technique Used

The final step in our model is the hiding step. In this step we
hide our data after encryption into a cover image to keep others from thinking that the secret information even
exists. In this paper we use one of the simplest algorithms of image
steganography which is the Least Significant bit algorithm (LSB). The technique
works by replacing the least significant bit of each pixel in the image by data
byte. After the cover image is transformed to bytes. LSB method generally
achieves both high capacity and high imperceptibility. 4 High capacity refers
to the large size of data can be embedded when compared to other techniques.
Imperceptibility refers to natural human ability to detect the difference
between the original object and embedded object. Replacing the least
significant bits seems to be a better option as the value they carry is insignificant
when compared to other bits. This concept is
represented in the Figure 4.3.

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