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I have a test encrypted file on my computer that when I run

gpg(2) --verify message.txt.asc

I get:

gpg: Signature made Tue Mar  3 21:16:41 2015 PST using RSA key ID *******
gpg: Good signature from "John Doe <[email protected]>"
gpg: WARNING: not a detached signature; file 'message.txt' was NOT verified!

And if I run

gpg(2) -d message.txt.asc

It does not prompt for the passphrase on my private key and yet still decrypts the gpg message. The other random .gpg/.asc files I have require that I decrypt them with a passphrase and --verify does not work.

What is the deal with the original file such that --verify works and I can decrypt without a passphrase? Is there a gpg command that analyzes a given file so I can gain context as to why it is not password protected? I thought it might be a detached signature (albeit without the default .sig extension) but there is a message in it as well. I do not have a gpg-agent running fwiw.

1 Answer 1

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So I think I figured it out. The file in question must have been created with just the --sign option and not both --sign --encrypt. Based on looking at the file relative to another that was both signed and encrypted, you can see they both have signatures but the file created with only --sign does not have a :encrypted data packet and only has the literal data packet:

(10:35) gpg > gpg --list-packets test2.txt.enc.asc
:pubkey enc packet: version 3, algo 1, keyid
    data: [2048 bits]

You need a passphrase to unlock the secret key for
user: "John Doe <[email protected]>"
2048-bit RSA key, ID ********, created 2015-02-28

:encrypted data packet:
    length: 405
    mdc_method: 2
gpg: encrypted with <a key>
:compressed packet: algo=2
:onepass_sig packet: keyid
    version 3, sigclass 0x00, digest 8, pubkey 1, last=1
:literal data packet:
    mode b (62), created 1463246548, name="test2.txt",
    raw data: 32 bytes
:signature packet: algo 1, keyid
    version 4, created 1463246548, md5len 0, sigclass 0x00
    digest algo 8, begin of digest 35 d8
    hashed subpkt 2 len 4 (sig created 2016-05-14)
    subpkt 16 len 8 (issuer key ID)
    data: [2045 bits]

Versus:

gpg > gpg --list-packets test2.txt.asc
:compressed packet: algo=1
:onepass_sig packet: keyid
    version 3, sigclass 0x00, digest 2, pubkey 1, last=1
:literal data packet:
    mode b (62), created 1463246421, name="test2.txt",
    raw data: 32 bytes
:signature packet: algo 1, keyid
    version 4, created 1463246421, md5len 0, sigclass 0x00
    digest algo 2, begin of digest b9 a7
    hashed subpkt 2 len 4 (sig created 2016-05-14)
    subpkt 16 len 8 (issuer key ID)
    data: [2047 bits]
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  • If it's not encrypted, just look at it with a text editor, or even hex editor. Running file on it should say if it's a pgp/gpg file or not too
    – Xen2050
    May 15, 2016 at 3:34

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