A PGP public key block: the shape

An armoured block whose marker lines announce that it carries a public key.

The shape

This is the family skeleton with PUBLIC KEY BLOCK written into both marker lines. Recognising it is a matter of reading two lines closely and then checking four properties of what sits between them.

Opening marker: five hyphens, BEGIN PGP PUBLIC KEY BLOCK, five hyphens
Word order: the three words PUBLIC, KEY, BLOCK, in that sequence, after BEGIN PGP
Case: upper case throughout the marker lines
Fields: optional; a name, a colon, a space, then free text
Separator: one empty line, immediately before the first body line
Body alphabet: base64 and nothing else, listed on the alphabets page
Line width: every body line the same width, except the last
Closing marker: the opening line with END in place of BEGIN

-----BEGIN PGP PUBLIC KEY BLOCK-----
Comment: example comment text

[body: 34 lines of base64 characters, removed here]
=xxxx
-----END PGP PUBLIC KEY BLOCK-----

The body is never shown on this site. A real one runs for dozens of lines of unbroken base64.

The hyphen count is worth stating plainly, because it is the rule most often broken by accident. Five on the left of the words, five on the right, on both the opening and the closing line. A block with four is not a variant; it is damaged.

Right shape

-----BEGIN PGP PUBLIC KEY BLOCK-----
Comment: example comment text

Wrong shape

----BEGIN PGP PUBLIC KEY BLOCK----
Comment: example comment text

Four hyphens instead of five, at both ends of the same line. Nothing else differs.

Right shape

Comment: example comment text

[body: 34 lines of base64, removed here]

Wrong shape

Comment: example comment text
[body: 34 lines of base64, removed here]

The empty line between the field and the body is gone. It is a separator with a job, not blank space that can be tidied away.

Inside the body there are no spaces, no tabs and no punctuation beyond the base64 set. Anything else, including a quote symbol at the start of a line or a stray full stop at the end, came from whatever moved the block rather than from the block itself.

Where you meet it

A public key block turns up printed into a page, saved as a file with an .asc ending, quoted underneath a message, or pasted into a field on a profile. The place changes what damage to expect, not what the shape has to be. Text pasted into a chat window tends to lose its line structure. Text quoted in a reply tends to gain a symbol at the front of every line. Text stored as a file usually arrives untouched, and the interesting question about a file is what its name claims, which belongs to a filename.

It is also common to meet the block and a fingerprint together, printed one above the other. That pairing looks like corroboration and is not; the point is made at a key fingerprint.

How to check it by eye

Four looks and a scan

Read the first line and count the hyphens at its left edge. Five. Then read the words: BEGIN PGP PUBLIC KEY BLOCK, capitals, in that order.
Jump to the last line and read it against the first. Same words, same hyphens, END instead of BEGIN.
Find the empty line. There should be exactly one, sitting above the first line of base64.
Track your eye down the right hand edge of the body. Those endings should form a straight column, with only the final line short.
Scan the body for a space. If you find one, the block has been through something that reformatted it.

What a wrong shape means

Almost always, it means the block was mishandled on the way to you. The list of things that mishandle armoured text is short and dull: reply quoting, message length limits, editors that reflow paragraphs, fields that strip empty lines, and selections made with a mouse that started one character late.

A ragged right edge in the middle of the body: the lines were rewrapped by something that thought it was helping.
A footer that is present but a header that is not: the copy began too far down.
No footer at all: the block was cut off, most likely by a limit on how much text the destination would take.
A symbol at the start of every body line: the block was quoted rather than copied.

What a wrong shape does not mean is that somebody has been caught doing something. Damage in transit and deliberate tampering leave the same marks, and the shape cannot separate them. The reasonable response to a broken block is to go back to wherever it came from and take a clean copy, then compare the two.

What a correct shape does not prove

Producing a well formed public key block requires no permission and no standing. It is an ordinary output of ordinary software. Everything below stays open after the format passes:

Whose key it is. The block contains no claim you can trust and the Comment field is free text typed by whoever made it.
Whether anybody holds the matching private half, or whether more than one person does.
Whether the key is current. A replaced or withdrawn key has exactly the same outer shape as a fresh one.
Whether the body is complete. Lines lost from the middle leave the markers and the line widths looking perfectly normal.
Whether the copy you are holding is the copy someone else was given, since two different blocks look identical at a glance.
Whether this key has any connection to the awazon darknet market. This site makes no statement of that kind about any key, and tests nothing.

The format check is a filter that removes broken text. It cannot remove text that is well formed and wrong, and well formed and wrong is cheap to make.

What this card is not

Nothing here describes verifying a signature, which is a different shape entirely and is set out at a clear signed message. The block that differs from this one by a single word has its own entry at a private key block. The base64 character set is not repeated here; it lives at alphabets, and the short hex string that identifies a key is at a key fingerprint.

A PGP public key block