Abstract: Securely transmitting a public key “PK” of a certificate holder within a public key infrastructure includes transferring a digital certificate signed with a digital certificate signature and having certificate holder and certificate key information from a sender “A” to a recipient “B”. The recipient “B” establishes a data-transferring connection to a digitally contactable resource “R” on the basis of resource identification information contained in the digital certificate and retrieves the public key “PK” of the certificate holder via the resource “R”. The recipient “B” compares a key hash value determined from the public key “PK” using a specified hash function with a certificate key hash value contained in the digital certificate and signed with a digital certificate signature. The public key “PK” assigned to the certificate holder is accepted and used by the recipient “B” if the determined key hash value matches the signed certificate key hash value.