I've just tried to compile the library on Mono/Linux, it builds, however with one glitch. The mentioned file is named HMAC.cs, but is referenced as Security/Cryptography/HMac.cs, so either reference or the file should be changed to both to be consistent. Otherwise builds and works fine, thanks for the lib.
Comments: ** Comment from web user: drieseng **
Comments: ** Comment from web user: drieseng **
Fixed in changeset 34612.
Thanks for the report!