The current invention describes a method for long term archiving of qualifiedly signed data in accordance with the current invention, which comprises the steps of hashing the data, encrypting the data through a cryptography algorithm, hashing the encrypted data, signing the hashed data with an advanced time stamp, generating a hash tree over the whole data file or the subgroups thereof and signing the hash tree(s) with a qualified time stamp. Furthermore, a computer system for conducting the method is disclosed.