Cryptographic circuit and data processing

A method for cryptographic data processing using a circuit, comprising:

• using a first circuit section of the circuit to perform a first cryptographic operation on data in order to obtain first cryptographic data, wherein the first circuit section is arranged in a secure area associated with a first resistance to attacks;
• transmitting the first cryptographic data to a second circuit section through a transmission area of the circuit that physically separates the second circuit section from the first circuit section, and wherein the second circuit section is in a less secure area with a second resistance to attacks that the first resistance to attacks associated with the first circuit section, and
• using the second circuit section of the circuit to perform a second cryptographic operation using the first cryptographic data in order to obtain second cryptographic data,
• wherein the second cryptographic data comprise a signature for other data, the method further comprising:
• generating the signature of the other data;
• and
• transmitting the other data with the signature from the second circuit section to the first circuit section and/or to an interface that is configured for communication with a third party;
• in the first circuit section, generating a short term third-party key using a shared key,
• wherein the first cryptographic data contain the short term third-party key;
• and
• wherein the short term third-party key is adapted to be applied to the other data that the second circuit section interchanges with the third party.