IDEA NXT

{{Short description|Block cipher}}

{{Infobox block cipher

| name = IDEA NXT (FOX)

| image = Image:Foxround.png

| caption = Round function of NXT

| designers = Pascal Junod, Serge Vaudenay

| publish date = 2003

| derived from = IDEA

| derived to =

| key size = 0-256 bits

| block size = 64 or 128 bits

| structure = Lai–Massey scheme

| rounds = 16

| cryptanalysis = Integral attack on 7 round NXT64 with time complexity of 2^237.4 and on 5 round NXT128 with time complexity of 2^205.6 by Wu Wenling, Zhang Wentao, and Feng Dengguo.{{cite journal |author1=Wu Wenling |author2=Zhang Wentao |author3=Feng Dengguo |date=25 August 2005 |title=Improved Integral Cryptanalysis of FOX Block Cipher |journal=Cryptology ePrint Archive |url=https://eprint.iacr.org/2005/292 }}

}}

{{Technical|date=November 2021}}

In cryptography, the IDEA NXT algorithm (previously known as FOX) is a block cipher designed by Pascal Junod and Serge Vaudenay of EPFL (Lausanne, Switzerland). It was conceived between 2001 and 2003. The project was originally named FOX and was published in 2003. In May 2005, it was announced by MediaCrypt under the name IDEA NXT. IDEA NXT is the successor to the International Data Encryption Algorithm (IDEA) and also uses the Lai–Massey scheme.{{cite web |title=IDEA NXT Technical Description |publisher=MediaCrypt |url=http://www.mediacrypt.com/_pdf/NXT_Technical_Description_0406.pdf |archive-url=https://web.archive.org/web/20070928014200/http://www.mediacrypt.com/_pdf/NXT_Technical_Description_0406.pdf |archive-date=28 September 2007 }} MediaCrypt AG holds patents on elements of IDEA{{cn|date=November 2016}} and IDEA NXT. The cipher is specified in two configurations: NXT64 (with block of 64 bits, key of 128 bits, 16 rounds) and NXT128 (with block of 128 bits, key of 256 bits, 16 rounds).