Using e-ID Number for Encryption and Digital Signing I want to use e-ID number for performing Encryption/Decryption and Digital Signing - and in order to do so, I've opted a PGP-oriented approach which goes a bit like this.


Generating PGP key-pair using e-ID Number (pass-phrase protected)
Digital Signing using e-ID Number (private-key) - and verifying the signature legitimacy by matching the sender's e-ID public-key fingerprint/key-id which has been pre-shared (via telephone/meeting) with the recipient.
Encrypting using e-ID Number (pre-shared) public-key of the recipient - and will then be Decrypted by using his/her private-key.


There will be a use of 'Random Session Key' for each session - as per the PGP concept and the implementation of classical (RSA, Elgamal) for Encryption/Decryption and (RSA or DSA) for Digital Signatures will be realized.

This is still a quite rogue approach - and therefore I would like you to share your view-point concerning the feasibility and the possible weaknesses of such a mechanism.

I will also appreciate other possible (effective) ways to use the e-ID card features for performing the Encryption/Decryption and Digital Signing - excluding the fact that card's electronic chip itself is equipped with a key-pair (by the reason of not being supported/compatible/encouraged for encryption and just for digital signing).
The number of your ID card is not really a secret, and probably shouldn't even considered one. You could use it as a key for symmetric encryption (but for this purpose you'd have to share it with your communication partners, and everybody knowing the ID could read the communication), but not for public/private key cryptography.

This is the reason why the cards often are (or can be) equipped with public/private key pairs, at least when they provide any cryptographic features.

An interesting way to work around the fact the basic key pair stored on the card is not really released to general usage is available for the German "Neuer Personalausweis" (the digital ID card issued for some years now): you can use the card to prove your identity to an OpenPGP key signing service (German website), which again will sign your key as certificate authority.


  Generating PGP key-pair using e-ID Number (pass-phrase protected)


Specifically discussing this point: If you want to use the card's identifier for generating the key, be aware that likely the key space is much smaller than necessary, which will heavily reduce the key's security. Brute-forcing the key might boil down to simply enumerating all possible IDs (which might be made harder using repeated hashing like often done for passwords). Also, everybody getting hold of the ID will be able to calculate the key without problems: the government, possibly also private entities getting hold of your ID card for verification purposes (hotels, airlines, ...).