Implementation of Present Cipher on FPGA for IoT Applications

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Implementation of Present Cipher on FPGA for IoT Applications

Anitha Kumari S Dr. Mahalinga V Mandi

    1. ech Scholar,ECE Professor Dept.of ECE

      Dr. Ambedkar Institute of Technology Dr. Ambedkar Institute of Technology Bengaluru, Karnataka, India Bengaluru, Karnataka, India

      Abstract In Internet of Things (IoT),lot of informations is being shared between the devices like smart houses,self driving cars etc. But the information is not protected as the Hackers can hack our system and also steal or change our information.In such circumstance there is a need for protecting the data using cryptographic algorithms.In this Paper a strong Encryption Cipher Called PRESENT which is an Ultra-Lightweight Symmetric Block Cipher is discussed as an application of PRESENT cipher,Text message encryption is considered.

      Keywords IoT, Lightweight Cryptography, PRESENT Cipher, FPGA.


        The need for Lightweight Cryptography is increasing now-a-days due to its flexible usage in constrained environment [1]. IoT mainly is a communication environment for RFID Tags and Sensor Nodes technology which are being used in home automation, Healthcare monitoring, structural monitoring etc. The incitation of Lightweight cryptography is to use less memory,less resources and less power supply to contribute for security as well as privacy solution [2].People in the present are surrounded by an environment which is completely dependent on smart devices.Smart devices are mainly dependent on RFID tags,Sensor nodes,actuators and IoT. As the number of smart devices increases the need for security also increases since it is constrained environment.In such condition a high security cryptographic primitive is needed

        ,One such example is Lightweight Cryptography.It is tailored mainly for the use in constrained environment.An high security cryptographic algorithm is needed for encryption and decryption of the information in Lightweight Cryptography,One such is Lightweight Symmetric Block Cipher called PRESENT CIPHER[1],[2].In this paper we will discuss the structure, working and implementation of PRESENT.

        The rest of the paper is organised as follows

        Section II discusses about PRESENT cipher, its Algorithm and Methodology..In Section III the Key Scheduling Algorithm of PRESENT is discussed.Section IV discusses the application of PRESENT Cipher for Text message encryption .Section V reviews the obtained Results.Finally In Section VI the paper is concluded.



        1. PRESENT Cipher

          PRESENT is an Ultra-Lightweight Symmetric Block Cipher.It was regulated in 2012 by The International

          Organization for Standardization/The international electro technical commission (ISO/IEC) suitable mainly for Lightweight Cryptography and it is also developed for implementation in constrained environment [1],[3],[4].The main objective of PRESENT Cipher is its extensive use in Lightweight environment such as RFID Tags,Sensor networks and IoT. It has gained popularity due to its Lightweight nature by providing high level of security in a very small environment with less area,less power,less resources and less memory.Hardware implementation Of Present Cipher is done using FPGA since it is cheaper,easier to use.,uses less power and its reconfigurability nature.

        2. PRESENT Algorithm and Methodology

          PRESENT is a 31 round Substitution-Permutation network (SPN) based block cipher with block size of 64-bit and 80 bit or 128 bit of key size [1],[2],[5].The 64-Bit keys are generated by internally processing the given 80-Bit input key at each round by the Key Scheduling Algorithm[5]

          .The input plain text is modified to obtain the encrypted Cipher text by application of confusion and diffusion over the data using three main operations at each round.They are

          1. AddRoundKey

          2. S-Box layer or Substitution Layer

          3. P-Layer or Permutation Layer

        The round function and the basic structure of a PRESENT cipher with 64 bit block size and 80 bit Key length is as shown in figure 1



        Fig. 1.(a) Round Function in PRESENT (b) Structure of PRESENT

        The three operations are performed as follows:

        1. AddRoundKey:It performs the bitwise EX-OR operation between the block of plaintext and the roundkey [1].

        2. Substitution Layer:It consists of substitution Box (S- Box) which is 4 bit to 4 bit [1] used for the input bit substitution [2].Here the length of the output bits and input bits has to be same.The S-Box table used for substitution is shown in table 1


        3. Permutation Layer:Bit permutations takes place in this layer or it is also just a mixing layer (rewiring) [6].Its operation is given by the following table 2 in which the ith bit of the state is moved to P(i) bit positions


        Previously we had discussed that PPESENT is a SPN based network.The SPN network is used to perform several mathematical operations in Block cipher algorithms.It applies several rounds of S-Box and P-Layer on the block of Plaintext and key given as input alternatively to produce cipher block.The structure of SPN is as shown in the figure 2.

        Fig. 2. SPN network


        PRESENT supports 80 bit or 128 bit key.In this project we concentrate on 80 bit key.In the Key Scheduling Algorithm initially the user-provided key is stored in the key register given as K.At round i the 64 bit round key is updated

        with the 64 Most significant bits of the current contents in the Key Register K [2],[7].It is given by

        Ki=k63 k62..k0 (1) Later the updation of Key register is as follows

        1. Rotating the bit positions of Key register by 61 times

        2. K18 k17 k16 k15 bits of the key register K are Exclusively-ORed with the value of the round counter with the round-counters LSB on the right

        3. The leftmost four bits are passed through the S-Box of PRESENT

        The Key scheduling and datapath block of the PRESENT cipher are shown in the below diagram

        Fig. 3. Datapath and Key Scheduling in PRESENT


        In the proposed Application text encryption and decryption is performed by taking input text message and EX-ORed with the cipher text key output of PRESENT cipher algorithm to obtain the encrypted text.This part performs encryption of the given text message.In the similar way decryption is also performed by EX-ORing the obtained encrypted text with the cipher text key output of the PRESENT cipher algorithm and finally the decrypted plain text is obtained.The Block diagram of the proposed system for text encryption and decryption is as shown in figure 4

        Fig 4. Encryption and Decryption of text message using PRESENT Algorithm



        The Simulation of the above proposed system was performed in Modelsim software using verilog coding language.The desired encrypted and decrypted text message

        using PRESENT algorithm was obtained and it is shown in the below figure

        Fig 5. Simulation result of PRESENT cipher for encryption and decryption

        of text message

        A plaintext of ASCII is considered and a 80 bit Hexadecimal key is considered.The encrypted message that is the Cipher text obtained is shown in figure 5.The same 80 bit hexadecimal key is used at decryption to get the Plain text back.

      6. Synthesis

        The synthesis of the proposed application was performed in Xilinx ISE 14.7 using Verilog coding language and the area,delay reports were obtained as shown in figure 6



        Fig 6. (a)Area (b)Delay report of PRESENT

        From the above obtained results it is clear that PRESENT utilizes less resource and delay is also minimum.

        Table 3 shows the Area,Frequency and path delay comparisons for different target devices


        Target device

        Area (Slices)



        Path delay (ns)













      7. Implementation of PRESENT on FPGA

      Present Cipher was implemented on Spartan 3 FPGA XC3S200-4TQG144C target device.The desired values for encryption and decryption of plaintext were obtained.The obtained value is shown in figure 7

      Fig 7. PRESENT implemented on FPGA for encryption and Decryption


      In the nearing future the need for Lightweight cryptography is very much necessary as billions of smart devices working on IoT environment are emerging.There has to be very high security in such constrained environment.Keeping this uppermost in mind a well developed cryptographic algorithm PRESENT is proposed.It is mainly tailored for lightweight cryptography in constrained environment.Present cipher is also very much advantageous compared to other cipher due to its less resource utilization,Performance and high security nature.In this paper the PRESENT Cipher algorithm was coded,Simulated,synthesised and implemented on FPGA successfully for encryption and decryption of text message..Different target devices were considered for comparison of area,frequency and path delay as shown in table 3.Among the three target devices Xc6slx45t-4-fqg484 utilizes less area of 149 slices,has a path delay of 4.983ns yielding frequency of operation of 200.6 MHz.


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