The need of special preservation of digital signed documents lay on the fact that the legal validity of a document signed today can deteriorate along the time due to different reasons, for example the discovery of vulnerabilities in the cryptographic algorithms, or simply the enhancements with time of calculation power may break just by force attack for the signatures with key length employed today. To address these problems there are already existing standards and signature formats like PADES, XADES or CADES.

Regarding preservation period, it depends on the document type, the business process or the legal regulation. For example some health records must be preserved for 50 years.

SiaCert provides an active archiving service dedicated to preserve the legal validity of signed documents along the time. This service (named Custody) is based on industry standards to guarantee interoperability and avoid vendor lock. Documents and the required metadata are stored in cryptographic modules (SIAVAL Custody) physically installed in high availability and redundancy in corporate grade data centers.

SIAVAL Custody provides an active archiving where long term signature standards are applied continuously, so that the legal validity of those documents can be delivered along the years. Furthermore the present Electronic Signature Regulation EU 910/2014 also established the signed data preservation as one of the Trust Service to be delivered by Trust Service Providers like SiaCert.

Legal validity of electronic signatures is explicitly described in different laws worldwide. For example in Spain there is the Law 59/2003, which stated the fact that any electronic signature can be admitted in legal processes. In Europe the Regulation 910/2014 already in place and that after a transitory period will remove all EU member legislation in regards to electronic identities and signatures, also state the same point. Nevertheless it is important to explain that not all electronic signatures have the same quality within a legal process. This is the reason why the EU Regulation establishes the conditions for Advanced and Qualified Signatures that are the ones with higher legal coverage. In this sense, the qualified signature has the same legal value as the handwritten signed document. The advanced signature may require some additional information (proofs) regarding the certificates and signature process.

SiaCert as Trust Service Provider fulfills the requirements for producing qualified signatures, but also guarantees  those additional pieces of information required for Advanced Signatures, like the integrity of the content, authenticity, identity of signatory, date and time (Timestamp) of the signature, etc. In this way signatory and/or companies have all available information for legal procedures.