A method for checking the validity of a digital document with use of a blockchain which is associated with a smart contract with program instructions, wherein a first block of the blockchain comprises a first entry associated with the digital document, wherein the first entry comprises a hash value of the digital document signed by an issuer of the digital document, wherein the issuer of the digital document confirms, with the signature, a successful verification of one or more details comprised by the digital document, wherein the method comprises: • receiving a read request to read the hash value of the digital document from the blockchain by a first blockchain server (100, 130) from a checking computer system for checking the digital document via a network, characterised in that the method furthermore comprises: • executing the program instructions of the smart contract by the first blockchain server (100, 130), wherein an execution of the program instructions of the smart contract comprises an entering of a second entry, signed by the checking computer system, into an additional second block of the blockchain, wherein the second entry indicates a checking by the checking computer system, • in response to the entering of the second entry into the additional second block of the blockchain, sending the hash value of the digital document, comprised by the first entry, to the checking computer system by the first blockchain server (100, 130) via the network to check a hash value calculated by the checking computer system for the digital document to be checked, wherein the digital document to be checked is acknowledged by the checking computer system as being valid if the hash value sent by the first blockchain server (100, 130) matches with the hash value calculated by the checking computer system for the digital document to be checked. wherein a first block of the blockchain comprises a first entry associated with the digital document, wherein the first entry comprises a hash value of the digital document signed by an issuer of the digital document, wherein the issuer of the digital document confirms, with the signature, a successful verification of one or more details comprised by the digital document, wherein the method comprises: • receiving a read request to read the hash value of the digital document from the blockchain by a first blockchain server (100, 130) from a checking computer system for checking the digital document via a network, • receiving a read request to read the hash value of the digital document from the blockchain by a first blockchain server (100, 130) from a checking computer system for checking the digital document via a network, characterised in that the method furthermore comprises: • executing the program instructions of the smart contract by the first blockchain server (100, 130), wherein an execution of the program instructions of the smart contract comprises an entering of a second entry, signed by the checking computer system, into an additional second block of the blockchain, wherein the second entry indicates a checking by the checking computer system, • in response to the entering of the second entry into the additional second block of the blockchain, sending the hash value of the digital document, comprised by the first entry, to the checking computer system by the first blockchain server (100, 130) via the network to check a hash value calculated by the checking computer system for the digital document to be checked, wherein the digital document to be checked is acknowledged by the checking computer system as being valid if the hash value sent by the first blockchain server (100, 130) matches with the hash value calculated by the checking computer system for the digital document to be checked. • executing the program instructions of the smart contract by the first blockchain server (100, 130), wherein an execution of the program instructions of the smart contract comprises an entering of a second entry, signed by the checking computer system, into an additional second block of the blockchain, wherein the second entry indicates a checking by the checking computer system, • in response to the entering of the second entry into the additional second block of the blockchain, sending the hash value of the digital document, comprised by the first entry, to the checking computer system by the first blockchain server (100, 130) via the network to check a hash value calculated by the checking computer system for the digital document to be checked, wherein the digital document to be checked is acknowledged by the checking computer system as being valid if the hash value sent by the first blockchain server (100, 130) matches with the hash value calculated by the checking computer system for the digital document to be checked.