# SIMECK-T: An Ultra-Lightweight Encryption Scheme for Resource-Constrained Devices
###### Abstract  
The Internet of Things produces vast amounts of data that require specialized algorithms in order to secure them. Lightweight cryptography requires ciphers designed to work on resource-constrained devices like sensors and smart things. A new encryption scheme is introduced based on a blend of the best-performing algorithms, SIMECK and TEA. A selection of software-oriented Addition-Rotation-XOR (ARX) block ciphers are augmented with a dynamic substitution security layer. The performance is compared against other lightweight approaches. The US National Institute of Standards and Technology (NIST) SP800-22 Statistical Test Suite for Random and Pseudorandom Number Generators for Cryptographic Applications and the German AIS.31 of the Federal Office for Information Security (BSI) are used to validate the output of the proposed encryption scheme. The law of iterated logarithm (LIL) for randomness is verified in all three forms. The total variance (TV), the Hellinger Distance (HD), and the root-mean-square deviation (RMSD) show values smaller than the required limit for 10.000 sequences of ciphertext. The performance evaluation is analyzed on a Raspberry PICO 2040. Several security metrics are compared against other ciphers, like \(\chi^{2}\) and encryption quality (EQ). The results show that SIMECK-T is a powerful and fast, software-oriented, lightweight cryptography solution. statistical test suite; lightweight cryptography; law of iterated logarithm; internet of things +
Footnote †: journal: Applied sciences  
0000-0002-4000-0000-0000-0000-0000-0000-0000-0000-0000-0000-00000-0000-00000-00000-00000-0000-00000-00000-000  
parametrizable parallel pseudo-random number generators [4] result in the creation of parallel stream ciphers [5; 6], but also in an increase in hardware production costs. It is a rare case for software implementations of encryption algorithms to use bit- or byte-level operations. This is because a read or write operation works on a block of data, and this situation means that carefully selected block ciphers the desirable solution. The introduction of the SPECK and SIMON family of block ciphers was a milestone for lightweight cryptography [7]. SPECK's design philosophy of prioritizing simplicity and efficiency influenced subsequent cryptographic work, making it a key reference point in the development of lightweight encryption algorithms. It demonstrated that strong encryption could be achieved with minimal resource consumption, which was crucial as the demand for security in constrained environments was growing rapidly. SPECK was second best in a survey covering 19 algorithms with different approaches to secure the Internet of Things [8]. [PERSON] et al. have shown that Addition-Rotation-XOR (ARX) ciphers are the preferred approach to secure resource-constrained devices [8]. Another notorious family of block ciphers is RC5 [9] and RC6 [10]. RC5 is a block cipher that has a variable word size, a variable number of rounds, and a variable-length secret key. An interesting feature of RC5 is the heavy use of data-dependent rotations [11]. In other words, the rotational operator depends on the plaintext. In our proposed implementation of the encryption scheme, the number of rounds is increased based on the supplied password. RC6 is an Advanced Encryption Standard (AES) candidate, using a 128-bit block. Such a block size is too large for resource-constrained devices. It is twice as slow as RC5 [9]. Improved RC6 (IRC6) [12] allows for a variable block size and relies on a layer of \"Permuted XORed Bytes\" (PXB) for the confusion/diffusion network. ROADRUNNER [13] is a cipher designed specifically for the 8-bit ATtiny45 microprocessor. The rapid increase in IoT applications implies an improved computational capacity for IoT hardware, meaning that 8-bit microprocessors are obsoleted by devices with a larger word size. The LED [14] block cipher is also hardware-oriented, offering a small silicon footprint. LED is a substitution box-oriented cipher that performs well with hard-coded lookup tables.