Questions about particular use cases (integrity verification w/o private key, add E flag to primary key, import secp256k1 key)

[s7r]

Hi list,

Please help me with some information and hints.

1. Is it possible, when transporting a message from Alice to Bob,
without holding any of their private keys, to do the following checks:
- verify the integrity of the message and make sure it is sanitized and
Bob can decrypt it with his private key;
- verify that the message was encrypted for Bob and not for anyone else
(Alice didn't mix recipients by mistake);


2. Is it possible to have just one key (the primary one, no subkey) with
E flag also (S,C,E) -- I know this is not recommended but this is a
particular use case and the risks are acknowledged. I guess gnupg will
not allow you to do this by default, but is there any magic that can be
done?


3. Is it possible to import a secp256k1 private key and use it? For
example a secp256k1 key in the following format:

0C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D

How could this be imported in gnupg?


4. Is there a way to skip the passphrase entirely and not encrypt the
private key at all?


Thanks.

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