A method and apparatus for encrypting data written to an Enterprise System Connection (ESCON) tape system and reading encrypted data from such a tape system and decrypting the encrypted data is described. One illustrative embodiment, in writing encrypted data to an ESCON tape system, receives from a computer over a first ESCON link a command to write a data block of specified size to the ESCON tape system; requests data constituting the data block from the computer in sub-blocks; compresses and encrypts each sub-block to produce a corresponding compressed and encrypted sub-block; and transmits to the ESCON tape system over a second ESCON link the compressed and encrypted sub-blocks using a series of chained-data write operations, the transmitted compressed and encrypted sub-blocks forming a compressed and encrypted data block on a tape of the ESCON tape system.