The SNOW family of stream ciphers, developed by Thomas Johansson and Patrik Ekdahl at Lund University, are word-based synchronous ciphers built around a 512-bit linear feedback shift register (LFSR) and a non-linear output state machine. The original SNOW 1.0 was submitted to the NESSIE project but was rejected after weaknesses were discovered, leading to the improved SNOW 2.0, which later became part of the ISO/IEC 18033-4 standard. A further modification, SNOW 3G, was created during ETSI SAGE evaluation to resist algebraic attacks and was adopted for the 3GPP encryption algorithms UEA2 and UIA2. However, researchers have found related-key attacks against both SNOW 2.0 and SNOW 3G. In 2019, the design was extensively redesigned as SNOW-V (and its tweak SNOW-Vi) to meet 5G network speeds, generating 128 bits per iteration by using 128-bit SIMD registers and the Advanced Encryption Standard (AES) round function for its output transformation.