Concepts

Signature Types According to Signature Structure

Signatures can be categorized into three classes according to the signature structure

Enveloping	The data takes place in the signature as XML or Base64.
Enveloped	The data contains the signature.
Detached (Ayrık)	Signature and the signed data are seperate from each other. Especially for large data this type of signature is suggested.

BES (Basic Electronic Signature)	The simplest form of signature with no timestamp
EPES (Explicit Policy Based Electronic Signature)	A special form of BES which includes policy signature information.
ES-T (Electronic Signature with Time)	EST signatures are created by adding a timestamp to a BES signature.
ES-C (Electronic Signature with Complete Validation Data References)	It is derived from ES-T by adding references to validation data.
ES-X (EXtended Electronic Signature)	Similar to ES-C,which additionally includes a timestamp over the validation references or the whole signed document.
ES-XL ((EXtended Long Electronic Signature)	Different from ES-C, it contains the validation data itself not the reference.
ES-A (Archival Electronic Signature)	A special form of signature which is protected by periodically generated timestamps against the danger of weakened cryptographich algorithms.