The invention relates to a cryptographic method for carrying out selective access control to attributes of a plurality of documents (102), which are associated with a first user (120), wherein the attributes are saved in one or more memories in a manipulation-proof manner. The method comprises: providing a non-linear personal document block chain structure (100), which is associated with the first user and comprises a plurality of linear block chain sub-structures (104, 108, 109, 110, 600), wherein each of the linear block chain sub-structures comprises a plurality of blocks which are linked to each other bidirectionally, wherein each of the documents comprises a plurality of attributes, which are saved distributed over a plurality of blocks of a secondary, document-specific secondary structure (106), which is associated with the corresponding document, checking access permissions of a second user (128) for access to the corresponding block and, in the case of a successful check, confirming the successful check for the second user, and, upon an access query of the second user, providing the confirmation of the successful check, granting access to the corresponding block for the second user.
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