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defining Session Key Computation parameters #18

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defining Session Key Computation parameters #18

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defining Session Key Computation parameters
Sakurann Oct 5, 2022
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defining Session Key Computation parameters
Sakurann Oct 5, 2022
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18 changes: 9 additions & 9 deletions main.md
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Expand Up @@ -251,7 +251,7 @@ TODO: Can we plan to register our service with Bluetooth SIG? This will allow us

ToDo: If 'Submit VC' latency is high due to the presence of a photograph we will fall back to the style that Kritina wrote with State.

ToDo: Check if there are conventions to the UUID. Original in ISO is `00000001-A123-48CE-896B-4C76973373E6`.
ToDo: Check if there are conventions to the UUID. Current UUID has been randomly generated.

## Identity Request

Expand Down Expand Up @@ -346,18 +346,18 @@ To calculate the session keys, the Wallet and the Verifier MUST perform ECKA-DH
The Verifier MUST derive session key using HKDF as defined in [RFC5869] with the following parameters:

* Hash: SHA-256
* IKM: Zab
* salt: SHA-256
* info: “SKVerifier” (encoded as ASCII string)
* L: 32 octets
* IKM: Zab // discuss
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@Sakurann Sakurann Oct 5, 2022

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* IKM: Zab // discuss
* IKM: Zab

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@Sakurann Sakurann Oct 5, 2022

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two pubkeys -> secret key -> input for IKM

* salt: SHA-256(???) // discuss
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@Sakurann Sakurann Oct 5, 2022 •
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* salt: SHA-256(???) // discuss
* salt: SHA-256(XOR(nonce, PubKey))

nonce is combination of pieces from both parties.

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@Sakurann Sakurann Oct 5, 2022

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plan to derive 16 bytes :)

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@Sakurann Sakurann Oct 5, 2022

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standard to XOR?

* info: “OpenID4VPVerifier” (encoded as ASCII string)
* L: 32 octets // discuss

The Wallet MUST derive session key using HKDF as defined in [RFC5869] with the following parameters:

* Hash: SHA-256
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@gsasikumar gsasikumar Oct 18, 2022

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Why did we choose SHA-256? Blake2b is a far better hashing algorithm and is performance friendly RFC 7693
. Note: Argon uses Blake2b .

* IKM: Zab
* salt: SHA-256
* info: “SKWallet” (encoded as ASCII string)
* L: 32 octets
* IKM: Zab // discuss
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@gsasikumar gsasikumar Oct 18, 2022

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IKM: Shared secret key created using RFC7748 for X25519.

* salt: SHA-256(???) // discuss
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@gsasikumar gsasikumar Oct 18, 2022

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salt: concatenate 8byte of nonce from the wallet and 8 bytes of nonce from relying party. So total of 16 bytes

* info: “OpenID4VPWallet” (encoded as ASCII string)
* L: 32 octets // discuss

For encryption AES-256-GCM (192) (GCM: Galois Counter Mode) as defined in NIST SP 800-38D or ChaCha20 RFC 8439 MUST be used.

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