## 2 Related Work
In each of the rounds, all the inputs include \"Left[\(i-1\)]\" and \"Right[\(i-1\)]\" which is derived from the previous round and sub-key Ki extracted from the 128-bit key K. The constant delta =0 \(\times\) 9E3779B9 is chosen to be \(2^{31}/\O\). This is to confirm that the sub-keys are distinct and that the accurate value of it does not have a cryptographic significance. In each round, the integer \"addition\" modulo of \(2^{32}\) is applied instead of XOR. The round function F uses addition, bitwise XOR, left and right shift operation. For the \(i\)-th cycle,  
\[\textit{Left [i]}=\textit{Left [i-1]}+\textit{F (Right [1-1], key [0,1], delta [i]),}\]  
\[\textit{Right [i]}=\textit{Right [i-1]}+\textit{F (Left [i-1], key [2,3], delta [i]),}\]  
\[\textit{Delta [i]}=\textit{Floor ((i+1)/2)*delta}\]  
Round function F is  
\[\textit{F(M,K[a,b],delta[i])}=\textit{((M<<4)AND k[a]) XOR (M AND delta[i]) XOR ((M>>5)AND k[b] ).}\]The 128-bit key is divided into four 32-bit blocks K=(k[0], k[1], k[2], k[3]) where odd rounds use keys k[0] and k[1] and even rounds use k[2] and k[3]. One cycle constitutes two rounds and the \(i\)-th round is shown in Figure 3.  
Many variations of the TEA algorithm have been proposed recently. [PERSON] et al. proposed an algorithm [44] that uses a combined asymmetric and symmetric encryption for secure file transfer. The security of the file is taken care by the symmetric algorithm TEA and security of the key by the asymmetric algorithm LUC based on Lucas function. But the method used the same key for all rounds of encryption leading to reduced security. [PERSON] et al. developed an SMS security system for mobile devices using the Tiny Encryption algorithm [45]. This system ensures that the confidential messages are encrypted in the presence of a key to obtain the encrypted SMS message that is sent to the destination mobile number. Cipher text at the receiver side can be decrypted using the same key to get the SMS. The drawback with this method is that the size of the SMS decides the encryption and decryption time taken for the process. XTEA is a block symmetric encryption algorithm that uses the Feistel structure [46]. This algorithm uses 64-bit block plaintext, 128-bit key and 64 rounds of encryption. This algorithm uses a more complex key-schedule than TEA with rearrangements of the shifts, XOR's and additions [47]. XXTEA, also called block TEA uses the same round function as XTEA but applies it cyclically across an entire message for several iterations [48]. Table 1 presents a summary of all the existing security algorithms. Figure 1: Encryption routine of the tiny encryption algorithm (TEA). Of all the discussed algorithms, TEA remains the most efficient for use in IoT networks for secure and quick transfer of text files between simple embedded devices. But one of the major issues with  
Figure 3: The \(i\)-th cycle of TEA. Figure 2: Decryption routine of TEA. TEA and its latest variations is the usage of same keys through all rounds of encryption, resulting in reduced security, which is evident from the avalanche effect of the algorithm. Also, the encryption and decryption time for text is high, leading to lower efficiency in IoT networks with embedded devices. This paper proposes a NTSA which provides enhanced security for the transfer of text files through the IoT network by introducing additional key confusions dynamically for each round of encryption.