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I have a version D TR-31 keyblock (which contains an AES Key for use in CMAC), and have the ZCMK key used, what is the method which I can use to extract the key from the TR-31 keyblock? I'll do my own development.

Maarten Bodewes
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Manuel Alcala
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2 Answers2

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This is specified in the TR-31 specification, namely ASC X9 TR 31-2018, Interoperable Secure Key Exchange Key Block Specification.

It is copyrighted so I cannot provide a better answer.

You can buy the document at the ANSI web store.

Jonathan Rosenne
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As another answer mentioned the standard is copyright unfortunately.

However there are open source implementions of TR-31 that can be used to learn how TR-31 works.

https://github.com/openemv/tr31

https://github.com/chhil/TR31Keyblock

Note also that TR-31 had been superseded with a nearly identical standard named ANSI X9.143.

See https://webstore.ansi.org/standards/ascx9/ansix91432022

The only difference in practice appears to be the mandate for key length obfuscation padding for AES and TDES keys.

satur9nine
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