A Compartive Study Between ( AES ) and ( DES ) Algorithms Based on the ( SET ) Protocol

Secure Electronic Transaction protocol is a very large protocol in securing electronic bargains in business online for the sake of privacy. The Data Encryption Standard (DES) cons are that it is slow and short key (56 Bits). The typical attack for this one is the key exhaustion, because of the progress in the computer devices. The goal of this paper is to offer a new perspective so the protocol is more secure and fast, by using (AES) Advanced Encryption Standard (128 Bits for 10 Round , 192 Bits for 12 Round, 256 Bits for 14 Round). Besides, it has a comparison between Data Encryption Standard & Advanced Encryption Standard.


Introduction
Online purchase is an essential part in e-business. E-commerce is one of most famous using in e-business part. That's to say you are selling and buying, but not in person, rather through the internet. Thus, you would pay online. Due to that, there is Secure Electronic Transaction protocol [1], [2]. This protocol is about security throughout the e-transaction.
Secure Electronic Transaction strong save protocol, which encrypts to enhance the transactions safety [3]. The online bargain begins this way, first the customer set wanted.
Second merchant answers by an order form that contains many relevant details, and overall an authorized certificate for him to show eligibility. Third, and as a result, the customer sends a buying a message, that contains payment related information [4]. Finally, the merchant verifies the customer and his credit card details to be shown, while the rest are encoded for the safety of the client. In Fig. 1 shown Participants in the SET system. This paper is organized as follows. In section 2: Secure Electronic Transaction Protocol, section 3: Data Encryption standard, section 4: Advanced Encryption Standard, section 5: valid secure electronic transaction protocol, section 6: security enhancement in secure electronic transaction protocol, section 7: comparative analysis of existing and enhanced secure electronic transaction.
Finally, section 8: is the conclusion.

Secure Electronic Transaction Protocol
SET is a very efficient security protocol, which uses encryption to supply secure information, guarantees payment safety, and authorize identity. In order to authenticate cardholders, merchants will be given digital certificates by certain institutions. It depends on encryption and digital certificate to confirm the security and authentication of the message, namely and commonly by the digital envelope. Using a randomly generated key, the message data is encoded by recipient's public key. This is known as digital envelope, where it is sent to the receiver's message encryption. The receiver uses a private key to decrypt the digital envelope, and it depends on reversing the original message by the symmetric key [5].

Data Encryption Standard
DES is actually the most used block cipher in the world. DES, it is a symmetric key algorithm for both sender and recipient secret key. There are many fields for DES; the most important of them is the banking industry. It is for this use that the DES was initially standardized, and ANSI ensures that it will be used in the next years and it will substitute DES with AES algorithms in the future. Although there is by whom over the design DES being used 56 bits key. DES is public standard; the design criteria used are categorized [6].
The block diagram of DES algorithm is shown in Fig. 2.

Substitution (Sub Bytes):
In the substitution steps uses a 16x16 lookup table in order to replace bytes with other given ones in the input state array. The creation of the table"s entries is done through the notion of multiplicative inverses in GF (2 8 ) and bit scrambling to destroy the bit-level correlations within each byte [7].

Shift Rows:
Every one of the four rows of the matrix is removed to the left. An entry that "fall off" is re-inserted on the right side of row. The shifting is performed as the following list indicates:

Add Round Key:
The 16 bytes of the matrix are currently measured as 128 bits and are XORed to the 128 bits of the round key. In the final round, then the output becomes the cipher text. Other than b 7 x 7 + b 6 x 6 + b 5 x 5 +b 4 x 4 + b 3 x 3 + b 2 x 2 + b 1 x+ b 0 = ∑ 8.1 Uses arithmetic in the finite field GF (2 8 ) with irreducible polynomial: m(x) = x 8 + x 4 + x 3 + x + 1 8.2 In Table 1 shows the compare between DES-56 Bits & AES-128 Bits processing time in min.

Conclusion
The Secure Electronic Transaction (SET) is a very vital procedure which is why it needs a strong defensive system is required. Thus the AES was designed after the development of the DES. AES uses (128 bits for 10 round, 192 bits for 12 round and 256 bits for 14 round); however, DES uses a 56-bit key. The confidentiality and authentication are more guaranteed with AES than it was with DES, additionally, the pace of encryption and decryption. Selected as AES finalist it has the following attributes: 1. 128-bit block size.
3. An iterative rather than a Feistal cipher (like IDEA).

5.
Has 9, 11, or 13 rounds, where each round consists of: wide range of platforms design simplicity from DES it is possible to say that AES algorithm is strong and will remain for several decades.