... time-memoryproductis 22k+1.7.38 Note (generalizedmeet-in-the-middletrade-off) Variations of Note 7.37 allow time-spacetradeoffs for meet-in-the-middle key search on any concatenation of L ... strengthened version of M-209 (C-48) with period exceeding 2.75 ×109(with keywheels of 47, 43, 41, 37, 31, 29pins); CD-55, a pocket-size version of the C-52; and T-55, an on-line version of the same,modifiable ... 22kkeypairs. The attack of Fact 7.33 reduces time from 22k, at the cost of substantial space.7.33 Fact For a block cipher with a k-bit key, a known-plaintext meet-in-the-middle attack de-feats double...