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Open PGP Signature Verification (OPSV)
OPSV is a FOSS solution for easy PGP signature verification.
OPSV is integrated in the larger keyoxide project and will therefore no longer be updated.
This project uses openpgp.js loaded in the browser, meaning all processing is done on the device itself and no data is ever sent to the server. It supports loading public keys directly through:
- plaintext input
- web key directory (WKD)
- HTTP Keyserver Protocol (HKP).
OPSV will always use the first input method it detects in the order described above.
It's also possible to not provide a public key. Read more about this in the
Using no public key at all section below.
Visit https://opsv.foss.guru/. On this website, you can enter a signed message (see example below) and any of the three supported public key inputs to verify that the owner of that public key was indeed the person to have signed that message.
Let's say I, Yarmo, would really like the world to know that I like pineapple. Using my private key, I've signed that statement so you can verify I wrote that message.
The signed statement:
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 I like pineapple. -----BEGIN PGP SIGNATURE----- iQJDBAEBCAAtFiEEog/Pt4tEmnyVrrtlNzZ/SvQIetEFAl70mVUPHHlhcm1vQHlh cm1vLmV1AAoJEDc2f0r0CHrRQXIP/08uza9zOtmZXv5K+uPGVzDKwkgPgZJEezX7 6iQ358f1pjSRvYfQ5aB13k2epUHoqCKArMYu1zPqxhvLvvAvp8uOHABnr9NGL3El u7UUgaeUNHkr0gxCKEq3p81abrrbbWveP8OBP4RyxmaFx13Xcj7mfDluiBHmjVvv WU09EdH9VPlJ7WfZ+2G2ZZDHuE5XiaeP7ocugTxXXLkp33zwpDX0+ZuCIXM6fQGe OccSffglFPdNBnfasuuxDWxTQPsEbWGOPJV+CAPmBDeApX+TBF9bovO3hw4Uozk2 VT7EAy8Hb0SOrUb3UNGxzoKv++5676IxyB4JXX0Tr9O4ZxhO8o9pEEHwirtn/J1+ MWven4gVlWM/6bMeUqx6ydyNc2nqF5059yfRmwGMlp09x82G4x1bcf6aDZ+5njDG fS5T2OpXRIkZHJx8BhmZjsxiDR0KV44zwHpt06+96ef3EDWB0BcP6M+a5Rtc33zf irRmQd2M6RLyXCYtdGIiiAFRuomw802U4F0P4LwVrZdbGA6ObqBv1k8BUFCMbMz8 Ab4hF7kO4z0Vh3JaKzcHey0pOzdNCPpAHZ51sAoAnFDM4PdMBgQxxVweCMu4KYMZ FN8sNn42oY/b7gDmwCelVhgD+rvUn/a8+B7CDmCp+wIquyrjrTt00voATcb+ZPMJ pTXJ/NcM =rqTX
Use this as "Signature" on OPSV.
Using plaintext public key
Now, let's check the signature. Go to my personal website and copy-paste the "plaintext" key in the "Public Key (1: plaintext)" field.
You will see a green message confirming that my key was used to sign this message. I really do like pineapple.
Using web key directory (WKD)
Remove the contents from the "Public Key (1: plaintext)" field. Now, in the "Public Key (2: web key directory)", write
firstname.lastname@example.org and verify the signature again. It is still verified. Try using
email@example.com or any other input, it won't verify.
Using HTTP Keyserver Protocol (HKP)
Remove the contents from the "Public Key (2: web key directory)" field. I uploaded my keys to the https://keys.openpgp.org/ HKP server, which is the default server used by OPSV. All you need to do is once again go to my personal website and copy-paste the "Fingerprint" in the "Public Key (3: HKP)" field (the second field!). Still verified!
Using no public key at all
Wait, what? Then what am I verifying the signature against?
PGP signatures can contain the
userId of the signer. If OPSV finds a
userId, it will use it to perform a HKP lookup.
Remove the contents from the "Public Key (3: HKP)" field. It again verifies BUT against the information contained within the signature itself. You should carefully check the information OPSV returns. In this case, the authenticity is confirmed because the
userId (firstname.lastname@example.org) matches the one I use.
The signature below does not contain a
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 I like pineapple. -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEog/Pt4tEmnyVrrtlNzZ/SvQIetEFAl70mT4ACgkQNzZ/SvQI etHUNBAAlswF4Q5IkPTsMELZPNHBps8CUJUeDWu3HlSz7c2U+4h2jJztHD0mDtxH PqKzUnqQqNF1Bot//5xoOcn+m6UaSCzDk1oQFwD6LlQA+ScnIXddoV3xLqzTRAMe dyuqOoDzoVeD+fWlwisnGElYX5jHRX6tgyKNh0auR3/crQUIJazAyeDwZFdJiwaL ntd+d8T0BcVlVVPYN7RIp1hpT+PLIcwIsr64Myfy8SOa4cjVcQgnrhR/Lfz9680T LCpnSohHRiA82nMGRiapEv+s+zy1NUZnVYbU2Li+Q0nYdSoDFu0xEBYmLOxwS50H j6kK0ZyRicNeq2T25aIlieliTmSFLHHpzi/Zw8Yt1+FtZvWf4pstA19ahk7AQK5W zYF2bMO2xn5D4/pRz1P4e2NTWYeIK+ZHttc7T9ZSS9Ffo03fjcJXhson3WcQZKB5 VIGVVFnlWujNYYotmxys84OtE6ePfVRwHasIOLfknVq64RVo68Y1Pgw/KPXSb1k6 3r+YD0mt5i/NWpwm79G/Aq54WI5JT905div88d0Bbpa3dScTZ2MiBJbP96pZBcKl dpm3RnjsbCFgZqEpclrEh2SD1e8eCjrNcouWK3jIfOkaWB2xk1KvNmdyQQTs3dkP /CpKcCJiNVvY9ogWxg9aUuQZUn4WvCvaEkmP4dfkk9s8yAKPQf8= =QqCq
Once again, the signature verifies. And again, it only verifies against the information contained within itself so that doesn't prove anything about its authenticity. Anyone can write this and the signature will return verified.
Except now, there is no
userId for easy manual verification. So, you need to either take the
keyId or the
fingerprint and find some other way of verifying it, for example by contacting the person who supposedly wrote the message.
In my case, you can simply visit my personal website and compare the
What can a bad actor do?
One could not sign a statement with my private key: I, and only I, have access to it.
One could however simply take any of my signed messages and change the content. Like so:
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 I like privacy invasion. -----BEGIN PGP SIGNATURE----- iQJDBAEBCAAtFiEEog/Pt4tEmnyVrrtlNzZ/SvQIetEFAl70la8PHHlhcm1vQHlh cm1vLmV1AAoJEDc2f0r0CHrRDcYP/R4Yo+xiBLHtrOEMAQQkwbxWyQgCbjS4h9iF As86o9a+t5dKSsL4gSoB3sdNAL0a1ZOhaAU8kWaR6xN1RvCQjFr878hEf631yai6 DfF2eRZPEsjXkAzlOKlPrAvtrNwUUMSDk20rGa4A9HHdxpfrmDRIgVaz3uNr1qqc N/Ag3OK/2l1pZFTqjPekqDnXwblLiuTTLFlMlS80LFKoa7zZLkE5SD5O6WQFpOK7 DwYJk1+UjWDgVugz8rSLWag0mag9Z815furPIkU9yRmE1tIjsgpCR+uJA/e0I4bn 4Ei0M29df1QucDNv6q2WoW/7rCMz1IY796TY/BbdqbFk6vOUUHu596mQB+fJDNTX jGC0SpJPhzhgoZICzK8yWJMJGoLXScYj95rCAqjYdnW/LDdAgODCyjSOxnzdI1zi prQf4OmayHzDjI8Bo4bl22toPdSIDt3r5MmSGXcmBrNU16ea7FC9MnR8dkKfHD55 tC3UL2Ps/iU76kqzGAei1PKvaVqKogUGi/kqWzfi2eg+useHRyZpJrJv3R2mE0Y2 eSLMMJ5cTuM60c0GSIPOxzBBsMRwa0HmEQ3HKgpnpkVYxoA00/hq91kuNavqUqM+ OyOgbb21woPAG+S4OCHkOINEAooeCfhpSFtmpa87sUcfvDHUuX1ivL4rYoQO3cT2 gNfjdSiB =tqZV
Given the wording of the statement, you naturally doubt the origin of it being me. You run it through OPSV and indeed, this is not what I wrote!
You know me, "I despise privacy invasion." (hint hint).