2. The client computer of claim 1 , wherein the suffix items form a partially ordered set in a first relation of the database, the partial order being formed with respect to the suffix items in non-encrypted form, the application program being operational to perform the steps of i. sequentially requesting and decrypting encrypted suffix items, wherein each request of the sequential requesting is performed by comparing the position of the update suffix item in the partial order with the position of the decrypted suffix items in the partial order, wherein the sequential requesting is performed until a position in the partial order for storing the update suffix item in the first relation is determined, ii. in case a position for storing the update suffix item in the first relation is determined, providing the storage request to the database, the storage request comprising the encrypted update suffix item and the position determined in step i).
2. The client computer of claim 1 , wherein the suffix items form a partially ordered set in a first relation of the database, the partial order being formed with respect to the suffix items in non-encrypted form, the application program being operational to perform the steps of i. sequentially requesting and decrypting encrypted suffix items, wherein each request of the sequential requesting is performed by comparing the position of the update suffix item in the partial order with the position of the decrypted suffix items in the partial order, wherein the sequential requesting is performed until a position in the partial order for storing the update suffix item in the first relation is determined, ii. in case a position for storing the update suffix item in the first relation is determined, providing the storage request to the database, the storage request comprising the encrypted update suffix item and the position determined in step i). 3. The client computer of claim 2 , wherein step i) comprises: a) requesting a current encrypted suffix item from the database, b) in response to said requesting of the current encrypted suffix item, receiving from the database the current encrypted suffix item, c) decrypting the current encrypted suffix item for obtaining a current decrypted suffix item, d) in case the update suffix item is located at a position in the partial order preceding the current decrypted suffix item, providing a request for determining the availability of a new encrypted suffix item in the first relation immediately preceding the current encrypted suffix item, e) in case the update suffix item is located at a position in the partial order succeeding the current decrypted suffix item, providing a request for determining the availability of a new encrypted suffix item in the first relation immediately succeeding the current encrypted suffix item, f) in case the new encrypted suffix item is available in the first relation, requesting the new encrypted suffix item and in response to said requesting receiving the new encrypted suffix item , and repeating steps c)-f) with the current encrypted suffix item in step c) being the new encrypted suffix item, g) in case the new encrypted suffix item is unavailable in the first relation, encrypting the update suffix item with the first cryptographic key for obtaining an encrypted update suffix item and providing the storage request of step ii) to the server, the storage request comprising the encrypted update suffix item and a position information, the position information instructing the server to store the encrypted update suffix item in the first relation at a position in the partial order immediately preceding or succeeding the position of the current encrypted suffix item, depending if the update suffix item is preceding or succeeding the current decrypted suffix item with respect to the partial order.