A method for recovering a first cryptographic key for decrypting an encrypted digital document by an issuer computer system of an issuer of the digital document, wherein the digital document, which is a digital copy of data of a physical document (100, 180), is saved in encrypted form under a first anonymised file name on a server, wherein a first copy of the first cryptographic key is further saved in encrypted form under a second anonymised file name on the server, wherein the encrypted digital document is decryptable with use of the first cryptographic key, wherein the first copy of the first cryptographic key is encrypted with a second public cryptographic key of a second asymmetric key pair assigned to the issuer of the digital document, wherein the second anonymised file name is calculated with use of a combination of personal attributes of the owner of the digital document, to which a one-way function is applied, wherein a second private cryptographic key of the second asymmetric key pair of the issuer is saved in a protected memory area of a memory of the issuer computer system, wherein the method comprises: • determining the second anonymised file name with use of the combination of personal attributes of the owner of the digital document by the issuer computer system, • establishing a first connection via a network between the issuer computer system and the server, • sending a read request to read the encrypted first copy of the first cryptographic key from the issuer computer system via the first connection to the server, wherein the read request comprises the determined second anonymised file name for identification of the encrypted first copy of the first cryptographic key on the server, • in response to the sending of the read request, receiving the encrypted first copy of the first cryptographic key by the issuer computer system from the server via the first connection, • decrypting the encrypted first copy of the first cryptographic key by the issuer computer system with use of the second private cryptographic key. wherein the digital document, which is a digital copy of data of a physical document (100, 180), is saved in encrypted form under a first anonymised file name on a server, wherein a first copy of the first cryptographic key is further saved in encrypted form under a second anonymised file name on the server, wherein the encrypted digital document is decryptable with use of the first cryptographic key, wherein the first copy of the first cryptographic key is encrypted with a second public cryptographic key of a second asymmetric key pair assigned to the issuer of the digital document, wherein the second anonymised file name is calculated with use of a combination of personal attributes of the owner of the digital document, to which a one-way function is applied, wherein a second private cryptographic key of the second asymmetric key pair of the issuer is saved in a protected memory area of a memory of the issuer computer system, wherein the method comprises: • determining the second anonymised file name with use of the combination of personal attributes of the owner of the digital document by the issuer computer system, • establishing a first connection via a network between the issuer computer system and the server, • sending a read request to read the encrypted first copy of the first cryptographic key from the issuer computer system via the first connection to the server, wherein the read request comprises the determined second anonymised file name for identification of the encrypted first copy of the first cryptographic key on the server, • in response to the sending of the read request, receiving the encrypted first copy of the first cryptographic key by the issuer computer system from the server via the first connection, • decrypting the encrypted first copy of the first cryptographic key by the issuer computer system with use of the second private cryptographic key. • determining the second anonymised file name with use of the combination of personal attributes of the owner of the digital document by the issuer computer system, • establishing a first connection via a network between the issuer computer system and the server, • sending a read request to read the encrypted first copy of the first cryptographic key from the issuer computer system via the first connection to the server, wherein the read request comprises the determined second anonymised file name for identification of the encrypted first copy of the first cryptographic key on the server, • in response to the sending of the read request, receiving the encrypted first copy of the first cryptographic key by the issuer computer system from the server via the first connection, • decrypting the encrypted first copy of the first cryptographic key by the issuer computer system with use of the second private cryptographic key.