This is a long list, and is therefore moved to a separate page. For clarification: the meaning of this list is to be complete. That is, it includes all authors that I am aware of who have ever written anything cryptographic (or has worked in data security). It does not concentrate on the top few people. An additional emphasis is put on young people, this can be seen from the citations per age column: I hope this helps to track down "young and talented and ambitious and ..." cryptographers. Finally, this list can be seen just as a yet another collection of cryptographer's addresses. Differently from others, it contains information about citations, PhD theses, etc.
This information is fetched from the previous list. It is definitely incomplete, so please let me know if my information about somebody's employer is misguided. The next table just takes the subtotal for institutions for which the number of citations is ≥1000 and the number of citations 2004+ is ≥500. (Those numbers can be adjusted.)
Does this list mean anything? It's up to yourself to decide. Just note that not everybody in this list is a cryptographer. Some are just crypto-related people. You must browse the list of cryptographers to find out if some place is strong by your definition. Finally, if two researchers coauthor a paper then this paper is going to add points to both of them. And often coauthors come from the same institution.
There are also some other statistical works out there. John R. Black orders the cryptographers by the number of papers in Eurocrypt and Crypto. Mihir Bellare takes only the 250 first authors in John's list and orders them according to ResearchIndex's "most cited authors" list (which compresses all authors that have the same initial and surname into one, for example, and is helpless with accented characters). Note that there are many famous people not in the first 250, like Bruce Schneier, Johan Håstad, Taher ElGamal, Niels Ferguson, Vincent Rijmen, Joan Daemen, Josh Benaloh, etc, some of which have done fundamental work in cryptography, but have been publishing in different venues (STOC/FOCS, FSE/PKC, etc.)