Python script to encrypt LS-Dyna input files
In LS-Dyna Encryption is most often used to encrypt material cards and the associated know-how. Since it is quite expensive to create material cards, a common way is to exchange material cards only in encrypted form. For the widely used *MAT_PIECEWISE_LINEAR_PLASTICITY_TITLE or *MAT_024, the know-how is based on the corresponding curves. Therefore this script encrypts only *DEFINE_CURVE{_TITLE} and *DEFINE_TABLE{_TITLE} by default.
According to Dynamore Germany, it is in principle also possible to partially encrypt the key files without completely encrypting the keywords. I was also able to test and confirm this myself. This will be added to this script in one of the next versions.
It is also possible to include an expiry date in the encryption. The *VENDOR keyword is used for this purpose. Unfortunately, it is not possible to encrypt a keyword only partially together with an expiry date. That is, if an expiry date is to be used, it is only possible to encrypt whole keywords.
This Python script is able to partially encrypt LS-Dyna input/key files based on the encryption algorithm provided by LSTC/ANSYS. 'gpg' is used for the encryption process. For more information on the general gpg encryption process, please refer to the GnuPG project at https://gnupg.org/. For more information on the encryption in the LS-Dyna enviroment please refer to these instructions. (https://ftp.lstc.com/anonymous/outgoing/support/FAQ/Instructions_encryption)
For example: For a *DEFINE_CURVE{_TITLE} keyword, it would be sufficient to encrypt only the x-y data of the curve to protect the know-how. Then the following keyword:
*DEFINE_CURVE_TITLE
$# title
Example Curve
$# lcid sidr sfa sfo offa offo dattyp
1 0 1.0 1.0 0.0 0.0
$# a1 o1
0.0 0.0
1.0 1.0
would look like this:
*DEFINE_CURVE_TITLE
$# title
Example Curve
$# lcid sidr sfa sfo offa offo dattyp
1 0 1.0 1.0 0.0 0.0
-----BEGIN PGP MESSAGE-----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=BJyZ
-----END PGP MESSAGE-----
But as already mentioned, this method does not allow you to specify an expiration date.
The keyword *VENDOR is intended only for an expiration date within an encryption. The usage is as follows:
*VENDOR
DATE 05/01/2024
This could be a self-written error message in the VENDOR keyword
*DEFINE_CURVE_TITLE
$# title
Exmaple Curve
$# lcid sidr sfa sfo offa offo dattyp
1 0 1.0 1.0 0.0 0.0
$# a1 o1
0.0 0.0
1.0 1.0
*VENDOR_END
This would allow the use of this then encrypted curve until May 1, 2024. Also the error message until the next *Keyword is printed in the message file or d3hsp. Please note that the LS-Dyna uses the server date to check against the expiration date. I.e. if you have an encrypted file, you can still run simulations with this encrypted file if you manually reset the server date to a date before the expiration date.
- Takes an inputfile and encrypts it.
- Keywords to encrypt can be selected (Default: *DEFINE_CURVE, *DEFINE_TABLE)
- Encryption key length 1024- and 2048-bit can be used (as provided by LS-Dyna)
- Expiry date can be selected
- Requires setup of gpg on the machine and importing the LS-Dyna Public keys
- These steps above are a one-time thing.
- Python3.6 and above
- Tested in various LINUX enviroments
- Not in Windows, but should work
At the moment this script is not yet available at PyPi. The plan is to make it available there eventually. For now, just download the script from its Github repo.It will definitely be distributed as a PyPi package once the package grows and does not contain just one file.
- On the CLI:
>>> python3 encrypt_lsdyna.py test.key
- As script (See also test_encrypt_lsdyna.py for this example.) Please note that all arguments must be keyword arguments.
from encrypt_lsdyna import LS_Dyna_Encryptor
lde = LS_Dyna_Encryptor(inputfile = 'test.key', expiry_date = '05/01/2024')
lde.encrypt_file()If you want to encrypt different keywords than the default ones, you can set them like this. The script will search if the keyword startswith the given keyword_to_encrypt. This can have some pitfalls and will need to be explored in more detail at a later date.
from encrypt_lsdyna import LS_Dyna_Encryptor
lde = LS_Dyna_Encryptor(inputfile = 'test.key', expiry_date = '05/01/2024')
lde.keywords_to_encrypt = ['*DEFINE_CURVE']
lde.encrypt_file()Since it is not possible to decrypt the encrypted key files without the private key, which only LS-Dyna has, the correct encryption can only be verified by an additional simulation run. Up to this point I never had any problems with the code, but please understand that I cannot take any responsibility or warranty. A simple way to check the encryption is to compare the unencrypted and the encrypted key file. The number of lines of the encrypted file should be greater than the number of lines of the unencrypted key file. The higher the encryption level (1024- or 2048-bit), the greater the difference. With the 1024-bit version, it turned out that the difference is not too big and the encryption really adds only a few lines.
Feel free to submit any issues or ideas for enhancement on the github page: python-lsdyna_encrypt/issues
Please take this as preferred way. I will come back to it as soon as possible.
If you feel the need and want to contact me directly via mail python.dyna@gmail.com or LinkedIn
I hope this is just the beginning of a Python package for LS-Dyna in particular and other CAE activities in general. I will expand the idea in the future. See Roadmap
- GnuPG as gpg
Currently None, but might change in the future. Maybe you're the one!
To be filled...
This code is licensed as open source under GPL-3.0 license which basically means you can do whatever you want with it. If you think there will be some issues with the licensing and your project, just reach out to me and I'm sure we will find a solution.
See RELEASE.md
To be filled, if some occur.
author: Julian J. Junglas
email: python.dyna@gmail.com
LinkedIn: LinkedIn