Methods for signing data and providing signed data, and associated terminal and server

A signed data provision method implemented by a terminal and including:

• sending a signature request for at least one data to a server via a network;
• obtaining a re-authentication key for the terminal from the network;
• receiving an encrypted signature;
• decrypting the encrypted signature with an encryption function shared with the server and by using a transport key calculated from the re-authentication key and at least one other authentication key for the terminal or for a user of the terminal to obtain a signature of said data calculated by using a private key associated with the terminal;
• and
• sending the signature to a third party device configured to verify validity of the signature with a public key associated with said private key.

A data signature server including:

• a secure element configured to obtain a signature of at least one data by using a private key associated with a terminal;
• at least one processor;
• and
• at least one non-transitory computer readable medium comprising instructions stored thereon which when executed by the at least one processor configure the data signature server to:
• receive a signature request for the at least one data sent by the terminal via a network;
• obtain a re-authentication key for the terminal from the network;
• encrypt the signature with an encryption function shared with the terminal and by using a transport key calculated from the re-authentication key and at least one other authentication key for the terminal or for a user of the terminal;
• and
• send the encrypted signature to the terminal.

A terminal including:

• at least one processor;
• and
• at least one non-transitory computer readable medium comprising instructions stored thereon which when executed by the at least one processor configure the terminal to:
• send a signature request for at least one data to a server via a network;
• obtain a re-authentication key for the terminal from the network;
• receive an encrypted signature;
• decrypt the encrypted signature with an encryption function shared with the terminal and by using a transport key calculated from the re-authentication key and at least one other authentication key for the terminal or for a user of the terminal to obtain a signature of said data calculated by using a private key associated with the terminal;
• and
• send the signature to a third party device configured to verify validity of the signature with a public key associated with said private key.