# HEADER_PLAINTEXT_LENGTH

> `const` **HEADER\_PLAINTEXT\_LENGTH**: `-65789` = `-65789`

Defined in: [packages/filecoin-encryption-envelope/src/cose/constants.ts:73](https://github.com/FilOzone/synapse-sdk/blob/bc8a4b093324ccef9b407251fcf4e91823c6f599/packages/filecoin-encryption-envelope/src/cose/constants.ts#L73)

`plaintext_length`, private use (RFC 9052 §3.1). Optional; written only
when the caller knew the content length before the envelope was emitted.

Being protected is what makes it a truncation check: an attacker can
neither edit it to match a short object nor strip it to escape the
comparison, since both change the AAD and fail every chunk tag.

Do not renumber this to `-65791`: see docs/tech-spec.md,
"`plaintext_length` and truncation".