Decode (CSNBDCO and CSNEDCO)

Use this callable service to decipher an 8-byte string using a clear key. The callable service uses the electronic code book (ECB) mode of the DES.

The callable service name for AMODE(64) invocation is CSNEDCO.

Considerations

If you have only a clear key, you are not limited to using only the encode and decode callable services.

You can pass your clear key to the clear key import service, and get back a token that will allow you to use the encipher and decipher callable services.
Consider using the Symmetric Key Decipher service (Symmetric Key Decipher (CSNBSYD or CSNBSYD1 and CSNESYD or CSNESYD1)).

Format

CALL CSNBDCO(
             return_code,
             reason_code,
             exit_data_length,
             exit_data,
             clear_key,
             cipher_text,
             clear_text)

Parameters

return_code

Direction	Type
Output	Integer

The return code specifies the general result of the callable service. ICSF and cryptographic coprocessor return and reason codes lists the return codes.

reason_code

Direction	Type
Output	Integer

The reason code specifies the result of the callable service that is returned to the application program. Each return code has different reason codes that indicate specific processing problems. ICSF and cryptographic coprocessor return and reason codes lists the reason codes.

exit_data_length

Direction	Type
Input/Output	Integer

The length of the data that is passed to the installation exit. The data is identified in the exit_data parameter.

exit_data

Direction	Type
Input/Output	String

The data that is passed to the installation exit.

clear_key

Direction	Type
Input	String

The 8-byte clear key value that is used to decode the data.

cipher_text

Direction	Type
Input	String

The ciphertext that is to be decoded. Specify 8 bytes of text.

clear_text

Direction	Type
Output	String

The 8-byte field where the plaintext is returned by the callable service.

Required hardware

This table lists the required cryptographic hardware for each server type and describes restrictions for this callable service.

Table 1. Decode required hardware
Server	Required cryptographic hardware	Restrictions
IBM System z9 EC IBM System z9 BC	CP Assist for Cryptographic Functions
IBM System z10 EC IBM System z10 BC	CP Assist for Cryptographic Functions
IBM zEnterprise 196 IBM zEnterprise 114	CP Assist for Cryptographic Functions
IBM zEnterprise EC12 IBM zEnterprise BC12	CP Assist for Cryptographic Functions
IBM z13 IBM z13s	CP Assist for Cryptographic Functions