1. A computer program product to allocate blocks of memory in a memory device having a plurality of blocks, the computer program product comprising a computer readable storage medium having computer readable program code including an application and an operating system embodied therein that executes to perform operations, the operations comprising: executing at least one unencrypted memory allocation function coded in the application to request allocation of unencrypted blocks in the memory device; executing an encrypted memory allocation function coded in the application to request allocation of encrypted blocks in the memory device, executing at least one unencrypted Input/Output (I/O) request function coded in the application indicating an I/O operation to perform against the unencrypted blocks in the memory device; executing at least one encrypted I/O request function coded in the application indicating an I/O operation to perform against the encrypted blocks in the memory device; executing the operating system to use an encryption key associated with the encrypted blocks to encrypt or decrypt data in the encrypted blocks to perform the encrypted I/O operation in response to processing the encrypted I/O request functions, wherein the unencrypted and encrypted memory allocation functions and unencrypted and encrypted I/O request functions comprise different functions in a library of functions available to the application.