Encryption hardware built on a network interface card is provided by the present invention for encrypting data sent from a computer to a network. A block of data is retrieved from the network interface card, encrypted using encryption hardware, and inserted into a data packet. A flag is set in the packet header to indicate the encryption type. If the data packet is received by a system equipped with similar network interface card, decryption algorithm indicated by the flag is applied to the data using decryption hardware on the network interface card. The decrypted data is sent to re-assembly logic to rebuild the original message for the transmitted packets. The original message is sent to a computer memory via a system bus for further processing. If the data packet is received by a system not equipped with the network interface card, suitable software is provided to decrypt the data packet.