2018/02/09 by P. Arun Babu, Babu, P. Arun, Jithin Jose Thomas +1
Computer Science · #Chaos-based Image/Signal Encryption #Coding theory and cryptography #Cryptographic Implementations and Security #Cryptography and Data Security #Cryptography and Security (cs.CR) #FOS: Computer and information sciences
paper · pdf · doi:10.48550/arxiv.1802.03201
openalex publication_date 2018/02/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
This paper introduces Freestyle, a randomized and variable round version of\nthe ChaCha cipher. Freestyle uses the concept of hash based halting condition\nwhere a decryption attempt with an incorrect key is likely to take longer time\nto halt. This makes Freestyle resistant to key-guessing attacks i.e.\nbrute-force and dictionary based attacks. Freestyle demonstrates a novel\napproach for ciphertext randomization by using random number of rounds for each\nblock, where the exact number of rounds are unknown to the receiver in advance.\nFreestyle provides the possibility of generating 2128 different\nciphertexts for a given key, nonce, and message; thus resisting key and nonce\nreuse attacks. Due to its inherent random behavior, Freestyle makes\ncryptanalysis through known-plaintext, chosen-plaintext, and chosen-ciphertext\nattacks difficult in practice. On the other hand, Freestyle has costlier cipher\ninitialization process, typically generates 3.125% larger ciphertext, and was\nfound to be 1.6 to 3.2 times slower than ChaCha20. Freestyle is suitable for\napplications that favor ciphertext randomization and resistance to key-guessing\nand key reuse attacks over performance and ciphertext size. Freestyle is ideal\nfor applications where ciphertext can be assumed to be in full control of an\nadversary, and an offline key-guessing attack can be carried out.\n