A method of data transfer and cryptographic devices

A data transfer method between a first security context (5) in a tenant system (1) and a second security context (7) in a service provider system (3), the method comprising: generating a list of access control that corresponds to the data in the first security context (5), where the access control list specifies that a valid use credential must be presented to allow a first type of use of the data; generate a first pair of cryptographic keys and a first cryptographic certificate in the second security context (7), the first pair of cryptographic keys comprising a first public key, KBLOB pub, and a first private key, KBLOB priv and the first cryptographic certificate comprising information from which the origin of the first KBLOB pub public key can be validated; send the first KBLOB pub public key and the first cryptographic certificate to the first security context (5); validating the first cryptographic certificate in the first security context (5); if the first cryptographic certificate is valid, encrypt the data and the corresponding access control list with the first public key KBLOB pub in the first security context (5); sending the data and corresponding encrypted access control list, and information from which the origin of the data can be validated, to the second security context (7).