Digital Signatures 
Digital signatures serve the same function for the processing of digital data as handwritten signatures do for paper documents.
You use digital signatures to sign digital documents. Digital signatures specifically identify the signer of a digital document and also protect the integrity of the document. Changes in signed documents are detected when verifying the digital signature.
Integration
You can use digital signatures in SAP systems either together with an external security product or without. By using an external security product with the SAP system, you can introduce features that are not directly available with the SAP system, such as digital envelopes or the authentication of individuals using smart cards.
However, for certain areas of application (for example, SAP ArchiveLink content server HTTP interface), the digital signature itself suffices without needing the extra features of an external product. For this reason, we deliver SAP Security Library (SAPSECULIB) with the SAP system.
For more information, see the documentation for the area of the application that uses the digital signature.