The DRACO Stream Cipher

In symmetric-key cryptography, we typically distinguish two types of encryption schemes: block ciphers and stream ciphers. Block ciphers divide a plaintext into blocks of a fixed size (e.g., 64 or 128 bits) and encrypt one such block of data as a whole. Stream ciphers, on the other hand, consider the plaintext as a continuous stream of data. The stream cipher maintains an internal state and in each step it outputs one bit or several bits and updates its internal state. The output bit stream is then combined with the plaintext, usually using the XOR operation. One advantage of stream ciphers is that their resource requirements are lower than those of block ciphers in many application scenarios. This makes them particularly useful in lightweight cryptography targeting resource constrained devices such as low-cost RFID tags.

In this blog post, we provide an overview over current developments in this area and introduce our new lightweight stream cipher DRACO, which was developed in cooperation with the Universität Mannheim (Alexander Moch, Matthias Krause) and the Universität Siegen (Vasily Mikhalev) and has recently been presented at FSE 2023 in Kobe, Japan.

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