User Exit CTDX029

The CTDX029 user encryption exit is located in the IOA LOAD library or MVS LINKLIST library. It must be loaded into the CSA during the subsystem start. In order to replace the user encryption exit, the CDAM subsystem must be stopped and restarted.

The CTDX029 user exit is activated for

• encryption - during the creation of a CDAM file that is specified for encryption by CTDX029
• decryption - during the retrieval of a CDAM file that was encrypted by CTDX029

The CTDX029 user encryption exit can be called with one of the following call functions:

• INIT
• PROCESS
• TERM

During the creation of a CDAM file, when CTDX029 is called, with the INIT function, it places a return code indicating that the file will

• be encrypted by the Control-D supplied CDAM Encryption routine
• not be encrypted, overriding other parameters specifications
• be encrypted by the Control-D supplied CDAM Encryption routine with a key supplied by the exit
• be encrypted by the exit

The return code indicator is saved in the CMP block. The indicator determines the method of decryption. Any administrative data that is returned is also saved in this block. During retrieval this data is accessible. The maximum length of this data is specified with the AMENCDLN parameter in CTDPARM.

If the last decision has been returned, the exit is called with the PROCESS function for each block, before the block is written to the file. The exit returns the encrypted data block and the length of encrypted data.

During the retrieval of a CDAM file, when CTDX029 is called, with the INIT function, it places a return code indicating that the file will be decrypted by the

• Control-D supplied CDAM Encryption routine with a key supplied by the exit
• CTDX029 exit

In the second case, the exit is called with the PROCESS function for each block, after the block is read from the file. The exit returns the decrypted data block and the length of decrypted data.

It is possible that the user exit algorithm will increase the length of the encrypted data. Use the AMENCFRE parameter in CTDPARM for specifying additional buffer length.

When the exit is called with TERM function, the exit releases all the resources that it used processing the file.

Since the user encryption exit must be completely backward compatible, it is possible to store the user exit version in the data for decryption process.

For more information about the AMENCDLN and AMENCFRE parameters, see the CDAM parameter descriptions in the INCONTROL Installation Guide: Installing.