The present description refers to a method for protecting data of a mobile agent (MA) from a first server (A) which are intended for at least one second server (B) within a network system against an attack and an unauthorized access, wherein the first server (A) as well as the at least one second server (B) have a pair of a public key (KA, KB) and a private key (PKA, PKB) associated therewith, respectively, the method comprising, starting from the first server, at least the steps of choosing an unique number (r0) and assigning it to the mobile agent (MA), choosing a secret symmetric key (SKo) and assigning it to the data (mB) to be protected, encoding the secret key (SKo) with the public key (KB) of the second server (B), encrypting the secret key (SKo) and the public key (KA) of the first server via a cryptographic wrapping function (h), thus forming a data authentication code (h(KA, SKo)), encoding the data (mB) with the secret key (SKo), and combining the unique number (r0), the encoded data ({mB}SKo) and the data authentication code (h (KA, SKo)) and encoding that combination with the private key (PKA) of the first server (A), thus forming a nested structure to be decoded successively for access to the data (mB).