Editing Block cipher (section)

===IDEA===
The ''[[International Data Encryption Algorithm]]'' (''IDEA'') is a block cipher designed by [[James Massey]] of [[ETH Zurich]] and [[Xuejia Lai]]; it was first described in 1991, as an intended replacement for DES.

IDEA operates on 64-bit [[block size (cryptography)|blocks]] using a 128-bit key and consists of a series of eight identical transformations (a ''round'') and an output transformation (the ''half-round''). The processes for encryption and decryption are similar. IDEA derives much of its security by interleaving operations from different [[group (mathematics)|groups]] – [[modular arithmetic|modular]] addition and multiplication, and bitwise ''[[exclusive or]] (XOR)'' – which are algebraically "incompatible" in some sense.

The designers analysed IDEA to measure its strength against [[differential cryptanalysis]] and concluded that it is immune under certain assumptions. No successful [[linear cryptanalysis|linear]] or algebraic weaknesses have been reported. {{As of|2012}}, the best attack which applies to all keys can break a full 8.5-round IDEA using a narrow-bicliques attack about four times faster than brute force.