IDEA
International Data Encryption Algorithm
A 64-bit-block symmetric cipher with a 128-bit key, historically used in early PGP.
IDEA is a symmetric block cipher that operates on 64-bit blocks with a 128-bit key and was notable for securing early versions of PGP email encryption. It is now largely of historical interest, superseded by AES for performance and its larger block and key options. For the exam, recognize IDEA as one of the named legacy symmetric algorithms rather than a current recommendation. Its small 64-bit block is a weakness for large data volumes compared with the 128-bit block of AES.
Looking IDEA up is step one. Getting tested on it is step two.
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