09-07-2011, 09:50 AM
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ABSTRACT
In the multimedia steganocryptic system, the message will first be encrypted using public key encryption algorithm, and then this encrypted data will be hidden into an image file thus accomplishing both data encoding and hiding. The multimedia data will be used to provide the cover for the information.
Cryptography involves converting a message text into an unreadable cipher. On the other hand, steganography embeds message into a cover media and hides its existence. Both these techniques provide some security of data neither of them alone is secure enough for sharing information over an unsecure communication channel and are vulnerable to intruder attacks. Although these techniques are often combined together to achieve higher levels of security but still there is a need of a highly secure system to transfer information over any communication media minimizing the threat of intrusion. In this paper we propose an advanced system of encrypting data that combines the features of cryptography, steganography along with multimedia data hiding. This system will be more secure than any other these techniques alone and also as compared to steganography and cryptography combined systems
Visual steganography is one of the most secure forms of steganography available today. It is most commonly implemented in image files. However embedding data into image changes its color frequencies in a predictable way. To overcome this predictability, we propose the concept of multiple cryptography where the data will be encrypted into a cipher and the cipher will be hidden into a multimedia image file in encrypted format. We shall use traditional cryptographic techniques to achieve data encryption and visual steganography algorithms will be used to hide the encrypted data.
CHAPTER 1
INTRODUCTION
In today’s information age, information sharing and transfer has increased exponentially. The threat of an intruder accessing secret information has been an ever existing concern for the data communication experts. Cryptography and steganography are the most widely used techniques to overcome this threat.
Cryptography involves converting a message text into an unreadable cipher. On the other hand, steganography embeds message into a cover media and hides its existence. Both these techniques provide some security of data neither of them alone is secure enough for sharing information over an unsecure communication channel and are vulnerable to intruder attacks. Although these techniques are often combined together to achieve higher levels of security but still there is a need of a highly secure system to transfer information over any communication media minimizing the threat of intrusion. In this paper we propose an advanced system of encrypting data that combines the features of cryptography, steganography along with multimedia data hiding. This system will be more secure than any other these techniques alone and also as compared to steganography and cryptography combined systems
Steganography is the art of “secret communication”. Its goal is to transmit a message (information) hidden inside another visible message. The typical visible message used in many steganographic systems is a digital image and the embedded message is usually hidden by working in the Fourier domain. The message is first coded by a sequence of small irregular images and then merged inside another image together with many other small images.
Visual steganography is one of the most secure forms of steganography available today. It is most commonly implemented in image files. However embedding data into image changes its color frequencies in a predictable way. To overcome this predictability, we propose the concept of multiple cryptography where the data will be encrypted into a cipher and the cipher will be hidden into a multimedia image file in encrypted format. We shall use traditional cryptographic techniques to achieve data encryption and visual steganography algorithms will be used to hide the encrypted data.
CHAPTER 2
LITERATURE SURVEY
2.1 Basic Overview on Cryptography
Cryptography involves converting a message text into an unreadable cipher.
A large number of cryptography algorithms have been created till date with the primary objective of converting information into unreadable ciphers The two types of algorithms that will be discussed are
• Joint Key Cryptography (Symmetric Key Cryptography): Uses a single key for both encryption and decryption
• Public Key Cryptography (Asymmetric Key Cryptography): Uses one key for encryption and another for decryption
2.1.1 THE JOINT KEY CRYPTOGRAPHY (Symmetric key cipher)
It uses a common key for encryption and decryption of the message. This key is shared privately by the sender and the receiver. The sender encrypts the data using the joint key and then sends it to the receiver who decrypts the data using the same key to retrieve the original message. Joint key cipher algorithms are less complex and execute faster as compared to other forms of cryptography but have an additional need to securely share the key. In this type of cryptography the security of data is equal to the security of the key. In other words it serves the purpose of hiding a smaller key instead of the huge chunk of message data
2.1.2 THE PUBLIC KEY CRYPTOGRAPHY (asymmetric key cipher)
It is a technique that uses a different key for encryption as the one used for decryption. Public key systems require each user to have two keys – a public key and a private key (secret key). The sender of the data encrypts the message using the receiver’s public key. The receiver then decrypts this message using his private key. This technique eliminates the need to privately share a key as in case of symmetric key cipher. Asymmetric cryptography is comparatively slower but more secure than symmetric cryptography technique. The public key cryptography is a fundamental and most widely used technique, and is the approach which underlies Internet standards such as Transport Layer Security (TLS). The most common algorithm used for secret key systems is the Data Encryption Algorithm (DEA) defined by the Data Encryption Standard (DES) [3]
2.1.3 A HYBRID CRYPTOSYSTEM
It is a more complex cryptography system that combines the features of both joint and public key cryptography techniques. We shall use traditional public key cryptography techniques to covert the message into a cipher. For embedding the cipher into images, a modified joint key technique will be used.
2.2 BASIC OVERVIEW ON STEGANOGRAPHY
Steganography is the art of hiding the existence of the communication message before sending it to the receiver. It has been practiced since 440 B.C. in many ways like writing information on the back of cattle in a herd, invisible ink etc. Some relatively modern ways include hiding the information in newspaper articles and magazines etc.
The objective of steganography is to hide a secret message within a cover-media in such a way that others cannot discern the presence of the hidden message. Technically in simple words “steganography means hiding one piece of data within another”. Modern steganography uses the opportunity of hiding information into digital multimedia files and also at the network packet level. Hiding information into a media requires following elements
•The cover media© that will hold the hidden data
•The secret message (M), may be plain text, cipher text or any type of data
•The stego function (Fe) and its inverse (Fe-1)
•An optional stego-key (K) or password may be used to hide and unhide the
message.The stego function operates over cover media and the message (to be hidden)
along with a stego-key (optionally) to produce a stego media (S).
