> 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-iseries-en/administracion-y-operacion/appendix-b.-cryptography-system-in-onesait-editran/introduction.md).

# Introduction

* The external key exchange mode, corresponding to Cryptographic Version 3.0 and 4.0. This mode uses cryptographic keys that are not exchanged by Editran. The keys will be exchanged between users. The possible alternatives are:
* DES symmetric keys, externally exchanged by the users, which allow DES encryption of the data (with the possibility of triple DES encryption for Editran version 5.0 or higher)
* Public and private keys using the RSA algorithm, externally exchanged, which support electronic signature of transmissions and:
* TD3C encryption of the data or higher). Cryptographic Version 3.0
* AES encryption of the data, with single, double, or triple key (for version 5.2 or higher). Cryptographic Version 4.0.

All the descriptions in this Annex (except for the encryption errors section) refer to the internal cryptographic management system in Editran. If the system is based on an External Key Management Interface, other documents describing how it works must be consulted.

In each Editran execution environment there must be a FICHKDES file, which contains the Host Master Key (HMK) of the installation, and where Exchange Keys or keys that encrypt keys reside, in which Editran needs to find a “local” or “exporter” key and another “remote” or “importer” key.

It is each Editran user entity's responsibility to maintain the file. For example, upon a change of HMK, the user entity will re-encrypt the keys in the CKDS so that they remain encrypted under the new HMK.

Editran cryptography includes bidirectional "online" encryption, unidirectional "batch" encryption, and "online" end-to-end authentication, where outgoing data are encrypted with a key that the receiving end must possess in order to decrypt them.

The Editran /P and Editran /G Cryptographic Profiles must match at both ends; otherwise, if the difference is in Editran /P the connection will not be established, and if it is in Editran /G the download will be halted.


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