A method of obtaining verification of authenticity of a maintenance means connected to a controller of a passenger transportation/access device of a building, said method being executed in said controller and comprising: receiving , a digitally signed license key from said maintenance means, said license key being digitally signed by a predetermined license means with a private asymmetric key of said license means, said digitally signed license key including a public asymmetric cryptography key of said maintenance means and a one-way hash of a unique identifier of said maintenance means, the unique identifier of the maintenance means including a serial number of a hardware component of the maintenance means; attempting to verify the validity of the digital signature of said received license key with a public asymmetric cryptography key of a predetermined license means; in response to said verification succeeding: extracting the public asymmetric cryptography key of said maintenance means from the received license key, generating a symmetric cryptography key, encrypting the generated symmetric cryptography key with the extracted public asymmetric cryptography key of said maintenance means, and sending the encrypted symmetric cryptography key to said maintenance means; receiving , from said maintenance means, the unique identifier of said maintenance means in an encrypted form; attempting to decrypt the received encrypted unique identifier of said maintenance means with the generated symmetric cryptography key; and calculating a one-way hash of the decrypted unique identifier of said maintenance means with a predetermined one-way hash function, comparing the received and calculated one-way hashes with each other, and in response to the received and calculated one-way hashes matching each other: determining the authenticity of said maintenance means to be verified. receiving , a digitally signed license key from said maintenance means, said license key being digitally signed by a predetermined license means with a private asymmetric key of said license means, said digitally signed license key including a public asymmetric cryptography key of said maintenance means and a one-way hash of a unique identifier of said maintenance means, the unique identifier of the maintenance means including a serial number of a hardware component of the maintenance means; attempting to verify the validity of the digital signature of said received license key with a public asymmetric cryptography key of a predetermined license means; in response to said verification succeeding: extracting the public asymmetric cryptography key of said maintenance means from the received license key, generating a symmetric cryptography key, encrypting the generated symmetric cryptography key with the extracted public asymmetric cryptography key of said maintenance means, and sending the encrypted symmetric cryptography key to said maintenance means; receiving , from said maintenance means, the unique identifier of said maintenance means in an encrypted form; attempting to decrypt the received encrypted unique identifier of said maintenance means with the generated symmetric cryptography key; and calculating a one-way hash of the decrypted unique identifier of said maintenance means with a predetermined one-way hash function, comparing the received and calculated one-way hashes with each other, and in response to the received and calculated one-way hashes matching each other: determining the authenticity of said maintenance means to be verified. <EOS>