Keyczar --- and other cryptographic libraries, mostly --- don't solve the issue of protocol design. They do let you choose the primitive you want, but it's stil

Keyczar --- and other cryptographic libraries, mostly --- don't solve the issue of protocol design. They do let you choose the primitive you want, but it's still up to you to pick a mode of operation, make sure you use authentication (AEAD mode / MAC), initialize IVs/nonces/counters correctly, etc. NaCl is very much a step in the right direction, but it's not an end-all solution either. Key management alone is a huge issue, for example, but virtually no library helps you out there beyond providing a basic toolkit. Of course, key management is very much in the realm of policy, so that's to be expected.