- Attest the state of a Linux computer

This app can verify signatures made with cryptographic-id-rs. When your computer is in a trustworthy state, you can generate a private key hidden in the TPM2 of your computer. This private key can be sealed with the current state of the computer (PCRs). Then the computer can only sign a message with this key when it is in the correct state according to the PCRs. For example, you can seal the key against the secure boot state (PCR7). If your computer is booting an operating system signed by another vendor, the TPM2 cannot unseal the private key. So if your computer can generate a correct signature, it is in this known state. This is similar to tpm2-totp but uses asymmetric cryptography. This means you do not need to keep the verification code a secret, but you can share it safely with the world.


- Verify the identity of a phone

You can generate a private key when your phone is in a trustworthy state. If your phone can create a correct signature, you know it is the same phone. Since the operating system can access the private key, the security guarantees are much weaker than with a TPM2. So the verification is just as secure as your phone. If you use Graphene OS, I recommend Auditor instead.


- Verify that a person is in possession of a private key

This works as the section above and has the same shortcomings. It can be used to verify someone in person when he sends his public key to you in advance.