ASCII armor.

What it is.

OpenPGP's native format is binary — compact byte sequences defined by RFC 4880 / 9580 that don't survive transit through systems that expect text. Email subjects, chat messages, copy-paste between apps, web forms — all of these can corrupt binary data by adding line wrapping, changing encodings, or stripping high-bit bytes.

ASCII armor solves this by encoding the binary as base64 (printable ASCII characters only), wrapping it in clearly-labeled BEGIN and END markers, and adding a CRC checksum so the decoder can verify the content wasn't corrupted in transit. The result is a self-contained text block that's safe to paste anywhere.

The BEGIN line identifies what's inside:

• -----BEGIN PGP MESSAGE----- — encrypted message
• -----BEGIN PGP SIGNED MESSAGE----- — clearsigned text
• -----BEGIN PGP SIGNATURE----- — detached signature
• -----BEGIN PGP PUBLIC KEY BLOCK----- — public key
• -----BEGIN PGP PRIVATE KEY BLOCK----- — secret key (sensitive!)

Why it matters.

Without ASCII armor, sharing PGP material through anything other than purpose-built tools would constantly fail. Email clients would corrupt binary attachments. Chat apps would strip null bytes. Copy-paste between applications would silently mangle the content. ASCII armor lets a public key fit in an email signature, a clearsigned announcement fit in a blog post, an encrypted message fit in any messenger.

The trade-off is size — base64 expands binary content by about 33%. For one-off messages that's nothing; for huge encrypted files, binary is more efficient. Most OpenPGP tools default to binary for files (.gpg) and ASCII armor for text operations.

Related terms

• Clearsigned message
• Detached signature
• Public vs private key
• OpenPGP standard