25C3 -

25th Chaos Communication Congress
Nothing to hide

Tor E. Bjørstad
Tag Day 3 (2008-12-29)
Raum Saal 3
Beginn 14:00
Dauer 01:00
ID 2875
Veranstaltungstyp lecture
Track Hacking
Sprache der Veranstaltung en

An introduction to new stream cipher designs

Turning data into line noise and back

Even with "nothing to hide", we want to protect the privacy of our bits and bytes. Encryption is an important tool for this, and stream ciphers are a major class of symmetric-key encryption schemes. Algorithms such as RC4 (used in WEP/WPA, bittorrent, SSL), A5/1 (GSM telephony), E0 (bluetooth), as well as AES in counter (CTR) mode, are important examples of stream ciphers used in everyday applications.

Whereas a block cipher such as AES works by encrypting fixed-length data blocks (and chaining these together in a suitable mode of operation), stream ciphers output an unique and arbitrary-length keystream of pseudorandom bits or bytes, which is simply XORed with the plaintext stream to produce the ciphertext. Advantages of stream ciphers often include smaller hardware footprint and higher encryption speeds than comparable block ciphers such as AES. However, cryptanalysis has led to attacks on many of the existing algorithms.

The ECRYPT Stream Cipher Project (eSTREAM) has been a 4-year project funded by the EU to evaluate new and promising stream ciphers. The project ended in April 2008, with a final portfolio which currently consists of 7 ciphers: 3 suitable for hardware implementation, and 4 aimed at software environments. The portfolio ciphers are considered to provide an advantage over plain AES in at least one significant aspect, but the designs are very different and often suited for different applications.

Since the eSTREAM ciphers are quite new, many of them are not well known outside the academic community. The goal of this talk is to give a very quick presentation of each of the 7 portfolio ciphers: Grain v1, MICKEY v2, Trivium, HC-128, Rabbit, Salsa20/12 and SOSEMANUK.

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