Challenges are no longer active
The RSA Security Secret-Key Challenge consisted of 13 contests in total, one using DES and the remaining 12 using the block cipher RC5 with a variable keysize. See "Status and Prizes" for the value of the prizes attached to the contests and for information about the final status of all contests.
In the case of DES, there were two further contests, culminating in DES Challenge III, which was solved in less than a day.
For each of the thirteen contests, there was a "real" contest for which cash prizes are awarded and a "test" pseudo-contest against which participants could test their software. The different contests are referenced by the contest identifier, which also serves to distinguish between the test and the real contests.