Embedded cryptographic system
First Claim
1. A cryptographic system (1) comprising first cryptographic algorithm means (2) for enabling cryptographic operations, input/output means (3, 4) for receiving input streams and sending output streams wherein said input streams are transformed to said output streams by said cryptographic operations, at least one test plaintext Pi and for each test plaintext Pi a corresponding test ciphertext Ci, receiving means (5) for receiving a control stream which is including at least one apoptosis key Ki, checking means (6) for checking whether said at least one test ciphertext Ci is the enciphered image of the corresponding test plaintext Pi under the cryptographic operation of said first cryptographic algorithm means (2) when using said apoptosis key Ki, switching means (7) for stopping said cryptographic operations with said first cryptographic algorithm means (2), wherein said stopping by said switching means (7) is triggered by said checking means (6).
1 Assignment
0 Petitions
Accused Products
Abstract
An embedded cryptographic system comprises at least one test plaintext/ciphertext pair Pi, Ci for which the key has been destroyed or stored at a very safe place. If at some later date, at least one apoptosis key Ki is presented to the cryptographic system which has the property that Ci is the enciphered image of Pi under Ki, then the algorithm could be broken and should not be used any more. Instead a more conservative algorithm should be used. The method for changing the ciphering by an embedded cryptographic system includes the step of checking whether at least one test ciphertext Ci is the enciphered image of a corresponding test plaintext Pi under a apoptosis key Ki and the step of switching off the used cryptographic mode or the step of switching to an other cryptographic mode in case of a positive checking result. In order to enable the step of checking a protocol has to define a control stream with at least one key to be checked. The checking will be done as soon as such a control stream is received by the cryptographic system. The advantage of this solution is the fact, that there is no need for controlling respectively trusting the manufacturer or a security service. The embedded cryptographic system can receive the key or a collection of keys {Ki} from anywhere.
-
Citations
13 Claims
-
1. A cryptographic system (1) comprising
first cryptographic algorithm means (2) for enabling cryptographic operations, input/output means (3, 4) for receiving input streams and sending output streams wherein said input streams are transformed to said output streams by said cryptographic operations, at least one test plaintext Pi and for each test plaintext Pi a corresponding test ciphertext Ci, receiving means (5) for receiving a control stream which is including at least one apoptosis key Ki, checking means (6) for checking whether said at least one test ciphertext Ci is the enciphered image of the corresponding test plaintext Pi under the cryptographic operation of said first cryptographic algorithm means (2) when using said apoptosis key Ki, switching means (7) for stopping said cryptographic operations with said first cryptographic algorithm means (2), wherein said stopping by said switching means (7) is triggered by said checking means (6).
-
5. A method for creating a cryptographic system (1) for carrying out cryptographic operations characterized by the steps of
implementing within said cryptographic system (1) a first cryptographic algorithm enabling said cryptographic operations, selecting at least one test plaintext Pi and enciphering each test plaintext Pi with said first cryptographic algorithm and with a corresponding apoptosis key Ki thereby generating a corresponding test ciphertext Ci for each test plaintext Pi, implementing within said cryptographic system (1) said at least one test plaintext Pi and for each test plaintext Pi said corresponding test ciphertext Ci, implementing within said cryptographic system (1) receiving means (5) for receiving a control stream which is including at least one apoptosis key Ki, implementing within said cryptographic system (1) checking means (6) for checking whether said at least one test ciphertext Ci is the enciphered image of the corresponding test plaintext Pi under said first cryptographic algorithm when using said apoptosis key Ki, implementing within said cryptographic system (1) switching means (7) for stopping said cryptographic operations with said first cryptographic algorithm, wherein said stopping by said switching means (7) is triggered by said checking means (6).
-
8. A method for operating a cryptographic system (1) for carrying out cryptographic operations characterized by the steps of
providing a first cryptographic algorithm for enabling said cryptographic operations, receiving input streams and sending output streams wherein said input streams are transformed to said output streams by said cryptographic operations, receiving a control stream which is including at least one apoptosis key Ki, checking whether a test ciphertext Ci is the enciphered image of a corresponding test plaintext Pi under said first cryptographic algorithm when using said apoptosis key Ki, stopping said cryptographic operations with said first cryptographic algorithm, if said test ciphertext Ci is the enciphered image of said corresponding test plaintext Pi under said first cryptographic algorithm when using said apoptosis key Ki.
-
11. A computer software product for operating a cryptographic system (1) for
carrying out cryptographic operations, said product is characterized by a computer-readable medium in which program instructions are stored, which instructions, when read by a computer, enable the computer to perform a first cryptographic algorithm that is enabling said cryptographic operations, receive input streams and send output streams wherein said input streams are transformed to said output streams by said cryptographic operations, receive a control stream which is including at least one apoptosis key Ki, check whether a test ciphertext Ci is the enciphered image of a corresponding test plaintext Pi under said first cryptographic algorithm when using said apoptosis key Ki, stop said cryptographic operations with said first cryptographic algorithm, if said test ciphertext Ci is the enciphered image of said corresponding test plaintext Pi under said first cryptographic algorithm when using said apoptosis key Ki.
Specification