> For the complete documentation index, see [llms.txt](https://docs.editran.onesait.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.editran.onesait.com/documentacion-editran/ibm-editran-v5.3-cics-en/key-manager/appendix/verification-of-exchanged-keys.md).

# Verification of exchanged keys

When 2 entities have used key exchange, they can validate as follows, in case cryptography fails:

* In editran, they must have the following values set: encryption = ‘s’, version = 3.0 or 4.0, suitable algorithms, and key interface (ZTBGBIGC for batch and ZTBPOIGC for online).
* If one end has SUBSISTEMA LOCAL=a and SUBSISTEMA REMOT=b set for a session, then on the remote entity they must have set the inverse value, that is, SUBSISTEMA LOCAL=b and SUBSISTEMA REMOT=a (the remote entity can use the local key and remote key fields, but it does not make much sense to do so).
* Once the above values have been agreed upon:
  * Querying the version and key sent in one direction.
    * The local end queries the subsystem it has with the remote entity, for example, subsystem 0 (option 6.3 for RSA and 6.4 for DES).
    * The remote end queries the SAME subsystem (option 6.4 for RSA).
    * On both ends, the same ACTIVE VERSION MUST APPEAR. If not, manually activate one, agreeing on both ends so that the same version remains active on both.
    * Select the version label (modulus-exponent calculation for RSA and encryption for DES). Both ends must “display” the same thing.
  * Querying the version and key sent in the opposite direction.
    * The remote end queries the subsystem it has with our entity, for example, subsystem 0 (option 6.3)
    * The local end queries the SAME subsystem (option 6.4).
    * On both ends, the same ACTIVE VERSION MUST APPEAR. If not, manually activate one, agreeing on both ends so that the same version remains active on both.
    * Select the version label (modulus-exponent calculation for RSA and encryption for DES). Both ends must “display” the same thing.


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