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book/source/07-signing_data.md
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@ -19,15 +19,14 @@ Note that signatures over data are distinct from {ref}`component_signatures_chap
## Signature types
Data signatures use one of two OpenPGP [signature types](signature_types):
OpenPGP data signatures use one of two [signature types](signature_types):
- "Signature of a binary document" (*Binary Signature*, type ID `0x00`): A universal signature type for binary data. Binary signatures are typically used for files or data streams.
Binary signatures are calculated over the data "as is", without performing any transformations.
- "Signature of a canonical text document" (*Text Signature*, type ID `0x01`): Used for textual data, such as email bodies. When calculating a text signature, the data is first normalized by converting line endings into a canonical form (`<CR><LF>`). The normalization mitigates issues caused by platform-specific text encodings, for example with detached signatures, where the message file may get re-encoded between signature generation and validation.
- **Binary signature** (type ID `0x00`): This is the standard signature type for binary data and is typically used for files or data streams. Binary signatures are calculated over the data without any modifications or transformations.
- **Text signature** (type ID `0x01`): Used for textual data, such as email bodies. When calculating a text signature, the data is first normalized by converting line endings into a canonical form (`<CR><LF>`). This mitigates issues caused by platform-specific text encodings, which is particularly important for detached signatures where the message file might be re-encoded between signature creation and verification.
Data signatures are generated by hashing the message content, plus the metadata in the signature packet, and calculating a cryptographic signature over that hash. The resulting cryptographic signature is stored in an OpenPGP signature packet.
Data signatures are generated by hashing the message content along with the metadata in the signature packet, and calculating a cryptographic signature over that hash. The resulting cryptographic signature is stored in an OpenPGP signature packet.
Data signature packets can be used in three different forms. We'll discuss these in the following section.
Data signature packets manifest in three distinct forms, which will be detailed in the subsequent section.
## Forms of OpenPGP data signatures