Difference Between TDES and SERPENT

Fahad Ashiq ⚡
7 min readOct 31, 2020


In this paper we will Clarify the beneficial coding of Serpent algorithm, Triple Data Encryption Standards (TDES), Verily often. In this summary we will evaluate the hierarchy and design of a new Advance Encryption Standard, on the basis of following standards:

· Friction over all known attacks exist is these algorithms.

· Enactment of code and speed on a broad range of platforms.

· Clearness of the design of the above-mentioned algorithms.

Other than this its same techniques and differences with the other ciphers and prominent advantages of a new AES with respect to DES and TDES, as well as its restrictions are investigated according to the same pattern mention above.


Trippel data Encryption Standard adopted by the National Institute of Technology (NIST) to replace existing data encryption standard (DES) as the most widely used encryption algorithm. Under the assistance of cryptographic research community in 1988, national institute of standards and technology (NIST) announced the acceptance of 15 candidate algorithms. In this research paper we present a candidate for Triple Data Encryption Standard. This analysis will include the initial characteristics, implementation characteristics and cost. After this analysis NIST reviewed the result of the research and selected the following algorithms in of them as for example SEPRENT, MARS, RC and TWOFISH as their finalists.

1. Appraisal for Criteria of Algorithms:

In September 1997 call for the candidate algorithms, NIST announced evaluation standard that would be used to distinguish the candidate algorithms. These standards were developed on the basis of public statements to Ref. and discussions at public Advanced Encryption Standard workshop held on April 15, 1997 at NIST. The evaluation criteria are divided into three major parts:

1.1 Security:

Security was the highly important components in the experiment and incorporated characteristics for example, in cryptanalysis algorithm will show friction, mathematical basis of the algorithm is sound, output of the algorithm must be spontaneous, and relative security as compared to other candidates.

1.2 Expense:

The second significant area of evaluation was expense that comprised regulations of authorizing, computational efficiency (speed), and requirements of memory. As one of National Institute of Science and Technology wants that the final Advanced Encryption Standard algorithm must be available worldwide on free basis, therefore public statements were wished on intellectual property assertions and on any potential confrontations. The speed of the algorithm is contemplated on assortment of platforms. During Round 1, the main concentration was on the speed associated with 128-bit keys. And on Round 2, both hardware performance and the speeds associated with the 192-bit and 256-bit key sizes were expressed. Memory regulations and software implementation constrains of the candidates were also important considerations.

1.3 Algorithm and Implementation Characteristics:

Algorithm and implementation characteristics were the third area of evaluation such as flexibility, suitability of hardware and software, and the simplicity of algorithm. Flexibility is the ability of an algorithm:

· To handle key and block sizes that must be supported.

· To work securely and efficiently in different types of environments.

· To be implemented as a hashing algorithm, stream cipher and to provide additional cryptographic services.

2. Triple Data Encryption Standard Algorithm:

Triple Data Encryption is founded on the Data Encryption Standard algorithm; therefore, it is very easy to modify occurring software to use Triple DES. It also has an advantage of substantiated reliability and a longer key length that eradicates many of the attacks that can be used to lessen the amount of time it takes to break Data Encryption Standard. However even this more influential of DES may not be strong enough to conserve data for long time (due in particular specific to the small block size). As such, the Data Encryption Standard algorithm itself has become ancient and is no longer used. [1]

2.1 Keys used in 3DES:

Triple DES using 3 different keys is still considered secure because there is no known attack which completely break its security to a point where it is feasible nowadays to crack. Private key is used to both encrypt and decrypt the data and is shared between the sender and receiver of encrypted data. The Public key is only used to encrypt data and to decrypt the data, the private key is used and is shared. The Public Key is free to use and the private key is kept secret only.

2.2 Usage of 3DES:

· It was one of the generally used encryption techniques before the rise increase of Advance Encryption Standard.

· It is accustomed in Finance payments and other private industry to encrypt data in transit and at rest including EMV Keys for conserving credit card transactions.

Flow Diagram of TDES

Source: https://www.geeksforgeeks.org/double-des-and-triple-des/

2.3 Restriction of Triple Data Encryption Standard Algorithm:

· Triple data Encryption standard is exposed to differential and related key attacks.

· it is also vulnerable to certain differences of meet-in- the middle attack.

3. Serpent Algorithm:

Serpent is a symmetric key block cipher that was a finalist in the Advanced Encryption Standard (AES) contest, where it was ranked second to Serpent was designed by Ross Anderson, Eli Bilham, and Lars Knudsen. The Serpent cipher algorithm is in the public domain and has not been patented. Serpent is one of the AES (advanced encryption standard) candidates and it has been implemented on various 8-bit, 16-bit and 32-bit platforms. In this paper, we have investigated various implementation options of Serpent on 24-bit DSP and described specific issues of the 24-bit platform. Today’s Digital Rights Management and secure audio distribution systems which and mostly works on the utilization of 24-bit DSPs and therefore efficient implementation of the encryption algorithm on such platform is very important. [1]

3.1 Working of Serpent Algorithm:

Serpent took a conservative approach to security opting for a large security margin the designers deemed sixteen rounds to be sufficient against known type of attacks but specified 32 rounds as insurance against future discoveries in cryptanalysis. The Official NATIONAL INSTITUDE OF SCIENCE AND TECHNOLOGY Reported as Advance Encryption Standard Competition classified serpent as having a high security margin along with MARS and Two Fish.

3.2 Round Functions:

Round function in serpent algorithm consist of three layers

· Key XOR operation

· As there are 32 rounds so, 32 parallel applications of one of the eight specified 44 S-boxes

· A linear transformation.

A second layer of key XOR replaces the linear transformation in the last round.

Flow Diagram of Serpent Algorithm

3.2. Usage of Serpent:

· The Serpent Cipher is considered to be stronger but also slow in speed.

· Everybody can use it in his software without any limitations.

3.3. Restriction of Serpent:

· There is no limitation of serpent but when we increase its round size it becomes slower.

· Due to 32-bit rounds and it will be more complex to you implement serpent on small blocks.

Tabular comparison of Serpent and Triple Data Encryption







Parallel Multiprocessing



Key Size increase/decrease

Three Times Increase then DES


Recursive Nature




64 Bits

128 Bits


168, 112 of 56 bits

128, 192 or 256 Bits


48 DES — Equivalent Rounds

32 Rounds


Feistel Network

Square 1995

First Published

1995 (RFC 1851)

21- 08 -1998

4. Theoretical Comparative Analysis of SERPENT and TDEA

4.1 Flexibility:

Flexibility means whether the algorithm is able to ride out with minor modifications according to the requirements.

4.1.1 Flexibility in Serpent:

Serpent keys are always to 256 bits. Which consists “1” bit followed by “0” bits.

4.1.2 Flexibility in TDES:

The Structure of TDES doesn’t support any modifications.










Summary of algorithms flexibility


Architecture tell us about the hierarchy and operation accomplished by an algorithm how to apparatus that algorithm and its characteristics. Architecture also assumes that whether the algorithm is symmetric or asymmetric make use of confidential key or public key for encryption and decryption.

Design of Serpent:

It is symmetric key algorithm in which fluctuation permutation network is used. There is 128-bit plain text and 32 rounds in serpent algorithm and key length of a serpent algorithm may vary in between 128, 192 and 256-bit.

Design of TDEA:

3DES is Precisely what it is named it accomplish 3 iteration of DES encryption on each block. As it is an advanced version of DES so is based on the concept of Feistel Structure The 3DES uses a 64-bit Plans text with 48-Rounds and a key length of 168 Bits permuted into 16 Sub-keys each of 48-bit length.


It has been observed that for 128-bit key size AES is much faster than Serpent. But the Encryption and Decryption time will vary in certain environment (i.e. it depends on the processor) and the amount of data needed to be Encrypt/Decrypt. In very high-speed processor, the Encryption and Decryption time will be less than that of the slower one. It also depends on the Programming language used for implementation. The presented simulation result shows that AES has better performance in Encryption/Decryption time than other algorithms used, it is a very secure encryption algorithms because it has a strong key but in some condition where the security is more important rather than Encryption/Decryption time, in that case Serpent is more secure than other Encryption algorithms.


1. Serpent: A Proposal for the Advanced Encryption Standard

2. Vocal Complete Design Solutions VOIP Voice Video Fax Data


3. [2]. R. Anderson, E. Biham, and L. Knudsen, Serpent: A Proposal for the Advanced Encryption Standard, AES algorithm submission, June 1998.



Fahad Ashiq ⚡

MCT and GOLD MLS Ambassador @ Microsoft ⚡| Ex SDG Lead @ Stacks Pakistan ✨ | Software Engineer 💻| Tech Enthusiastic 🚀 | Mentor @ MLSA Community Lahore 👨‍💻