The Stream Cipher Polar Bear
Johan Hastad Nada, Mats Näslund · 2005
We propose a new st am cipher called "Polar Bear". It combines const ruct ions used successfully inot her sit uat ions. The key init ializat ion uses Rijndael,t st dy st t uses a dynamic t ble as in RC4 and we guarant e a long periodt ught he use of a linear feedback shift4 gist r. The e#ciency for short messages is bet t ert hant hat of RC4 while for long messages Polar Bear is about afact ort wo behind in e#ciency. On t he ot her hand,we believe our const ruct ion has a larger safet y margin comparedt o RC4. 1 Introducti There is a big in3[[W y deman d for secure an d e#cien t stream ciphers, the mobile /wireless commun ication sector bein g on e of the foremost "con sumers" of such ciphers. The fact that stream ciphers don ot expan d messages, are toleran t to bit-errors , etc, are desirable properties for use withn arrow-ban dwidth wirelesslinl an voice codersdesign4 to perform well in thepresen8 of a few bit errors. rom scien tific poin t of view, there is also an in terest to get a better uner stanF3W for how to design stream ciphers, sinfl man y of the proposed schemes in the past have been more or less severely attacked. In respon se to the NESSIE call for primitives a few years ago, an umber of stream cipher proposals were submitted, butn n "survived"sinA the there was a feelin g thatn on e of the proposals was su#cien tly securean d e#cien t. The IST 6 P ECRYPT Network of ExcellenF has n w therefore issued an ew open call,n w directedonc towards stream ciphers. In this paper a stream cipher is presen tedin respon se to this call. The cipher has been design ed with goals: # Work described here has in part been supported by the Commission of the European Communities through the IST program under contract IST-2002-507932. The information in this document is ...