Techniques are disclosed for in-line storage of message authentication codes with respective encrypted data blocks. In one aspect, a given data block is encrypted and a message authentication code is generated for the encrypted data block. A target address is determined for storage of the encrypted data block in a memory. The target address is then modified to permit in-line storage of the message authentication code with the encrypted data block in the memory, and the encrypted data block and the message authentication code are transferred to the memory for storage at the modified address. Illustrative embodiments of the techniques advantageously facilitate secure off-chip storage of data in a processing system.