GlobalPlatformPro How to do key diversification

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I have a bunch of GlobalPlatform 2.2.1 JavaCards which I (currently) manage using GlobalPlatformPro. I want to lock them using PSKs like gpp -lock PSK.

However, I want to use individual PSKs for each card so I could give the PSK to the cardholder upon request (so they can install applets of their choosing). Ideally, I would derive the PSKs from a combination of a master key and the card UID (or AID or combination of both etc.) using a key derivation algorithm.

I noticed that gpp has the --lock-kdf-option but I couldn't find any documentation on it except the --help output: "Use KDF with lock key".

  • Is gpp in fact capable of this type of key diversification e.g. like AN10922, Visa2, EMV-CPS..? or should I use different/additional tooling for that?
  • Can I use gpp -lock-kdf MASTERKEY just like -lock but with the increased security of different keys being used for each card?
  • Would I then use gpp -key-kdf MASTERKEY to manage the card analoguous to using -key?
  • How can I obtain the diversified PSK for a card locked this way to give to the card holder without compromising the security of other cards?
globalplatform smartcard javacard lifecycle security
1 Answers

With the help in the comments and the realization that gpp has a wiki I'm starting to be able to answer some questions:

GlobalPlatformPro, like most GlobalPlatform implementations supports different algorithms for key diversification (namely emv, visa2, kdf3) as documented here, e.g.

gpp -lock emv:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Warning: no keys given, defaulting to 404142434445464748494A4B4C4D4E4F
Looking at key version
YYYYYYYYYYYYYYYY locked with: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Keys were diversified with EMV and ZZZZZZZZZZZZZZZZZZZZ
Write this down, DO NOT FORGET/LOSE IT!

With the new syntax, in gpp using a diversified key works just like with a static key except diversification algorithm has to be specified like emv:

Remains the question how to know the PSK of an individual card that was locked using a diversified master key. Please correct me if I'm wrong but this isn't possible because diversified keys are not static. Note how the emv-diversified keys differ for the lock and unlock procedure and how unlocking with the enc/mac/dek-keys generated for locking fails:

$ gpp -verbose -lock emv:$(cat master_key)
…
Warning: no keys given, defaulting to 404142434445464748494A4B4C4D4E4F
[INFO] GPSession - Using card master keys with version 0 for setting up session [MAC] 
[INFO] GPSession - Diversified card keys: ENC=404142434445464748494A4B4C4D4E4F (KCV: 8BAF47) MAC=404142434445464748494A4B4C4D4E4F (KCV: 8BAF47) DEK=404142434445464748494A4B4C4D4E4F (KCV: 8BAF47) for SCP02
…
A000000003000000 locked with: …
Keys were diversified with EMV and …
Write this down, DO NOT FORGET/LOSE IT!
$ gpp --unlock --key-enc 404142434445464748494A4B4C4D4E4F --key-mac 404142434445464748494A4B4C4D4E4F --key-dek 404142434445464748494A4B4C4D4E4F
Failed to open secure channel: Card cryptogram invalid!
…
$ gpp -verbose -unlock -key emv:$(cat master_key)
…
[INFO] GPSession - Using card master keys with version 0 for setting up session [MAC] 
[INFO] GPSession - Diversified card keys: ENC=89EF06C10723B737246259BE40B918C3 (KCV: 787239) MAC=49913E9A80E1B6128AF6C3AAEF0B6062 (KCV: D52C48) DEK=E63A8D78628F2E0FA6B4AC73669087DD (KCV: D1F762) for SCP02 with EMV
…
Default 404142434445464748494A4B4C4D4E4F set as key for …

Apparently, my question lacks basic understanding of how this type of key diversification works. To achieve what I want, I guess I will either have to "diversify" (in a non-globalplatform sense) static keys myself (e.g. using openssl -hmac) or simply generate per-card random keys and keep them safe in a list/database.

I'm now looking for tooling that supports key management in any such manner and one candidate I found is pyresman which can apparently manage/select keys and excecute GPshell scripts but hasn't been updated for four years.

user_48668650
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