[BUG] Cannot unlock KeePass DB on iOS with YubiKey 5C NFC (works on macOS via USB-C)

[Jmacek]

Preliminaries
I have ensured that:

• I am running the latest version of Strongbox on the App Store
• I have performed a full restart of my device

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Versions

On macOS:

• OS: macOS 15.3.2
• Strongbox Version: 1.60.36

On iOS:

• Device: iPhone 15 Pro
• OS: iOS 18.3.2
• Strongbox Version: 1.60.36 (Pro)

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Describe the Bug

I cannot unlock a KeePass database on iOS using my YubiKey 5C NFC, despite using the correct master password and having the YubiKey configured with the challenge-response secret in Slot 1.

On iOS, after entering the password and scanning the YubiKey via NFC, I receive the error:

"The credentials were incorrect for this database."

The exact same password, database file, and YubiKey do work on macOS (via USB-C), so the issue is isolated to NFC use on iOS. This has worked previously with the same yubikey and same database on this device.

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To Reproduce

1. Open Strongbox on iOS
2. Tap the database that uses YubiKey challenge-response
3. Enter the master password
4. Scan the YubiKey 5C via NFC
5. Receive the error: "The credentials were incorrect for this database."

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Expected Behavior

The database should unlock successfully after scanning the YubiKey via NFC, just as it does on macOS with USB-C.

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Additional Context

I created a virtual backup YubiKey using the same challenge-response secret, and it does unlock the database successfully on iOS. This confirms the master password and database config are correct, and points to an issue with Strongbox handling the physical YubiKey over NFC.