Method and programmable hardware security module
A programmable hardware security module, a method for securing a private key of a cryptographic key pair, and a method for securely providing a private key of a cryptographic key pair on a programmable hardware security module, wherein with the described devices and methods, a decentralised PKI is built, via which device keys and device certificates can be generated and target devices can be provided securely, where in this regard, the key-pair-specific transport key plays a central role in protecting the generated private key that is to be transferred, and where this is linked to the particular key pair intended for a target device via a key derivation from a master key utilizing a key-pair-specific derivation parameter.
1. A programmable hardware security module, comprising:
an application device for generating a cryptographic key pair;
a memory area having a master transport key;
a key derivation module for deriving a key-pair-specific transport key from the master transport key via a key-pair-specific derivation parameter which is generated once for every derived key-pair-specific transport key such that all derived key-pair-specific transport keys for different cryptographic key pairs differ among one another; and
a device for generating a digital certificate comprising a public key of the cryptographic key pair and including identification data of the programmable hardware security module, the digital certificate being simultaneously generated upon generation of the cryptographic key pair;
wherein the key-pair-specific transport key is utilized to encrypt a private key of the cryptographic key pair.
2. The programmable hardware security module as claimed in claim 1 , further comprising:
an output unit for outputting the private key as an encrypted file.
3. A corresponding programmable hardware security module, comprising:
a reception device for receiving a private key of a cryptographic key pair as an encrypted file and a digital certificate comprising a public key of the cryptographic key pair;
a memory area having a master transport key;
a key derivation module for deriving a key-pair-specific transport key from the master transport key via a key-pair-specific derivation parameter which is generated once for every derived key-pair-specific transport key such that all derived key-pair-specific transport keys for different cryptographic key pairs differ among one another; and
a device for generating a digital certificate comprising a public key of the cryptographic key pair and including identification data of the corresponding programmable hardware security module, the digital certificate being simultaneously generated upon generation of the cryptographic key pair;
wherein the key-pair-specific transport key is utilized to decrypt the encrypted file.
4. The corresponding programmable hardware security module as claimed in claim 3 , further comprising:
an interface for transferring the key-pair-specific transport key to a target device.
5. The corresponding programmable hardware security module as claimed in claim 3 , further comprising:
an interface for transferring the private key to a target device.
6. A method for protecting a private key of a cryptographic key pair, comprising:
generating the cryptographic key pair on a programmable hardware security module;
deriving a key-pair-specific transport key from a master transport key via a key-pair-specific derivation parameter which is generated once for every derived key-pair-specific transport key such that all derived key-pair-specific transport keys for different cryptographic key pairs differ among one another;
encrypting the private key using the key-pair-specific transport key; and
generating a digital certificate comprising a public key of the cryptographic key pair and including identification data of the programmable hardware security module, the digital certificate being simultaneously generated upon generation of the cryptographic key pair.
7. A method for securely providing a private key of a cryptographic key pair on a corresponding programmable hardware security module, comprising:
receiving the private key as an encrypted file and a digital certificate comprising a public key of the cryptographic key pair and including identification data of the programmable hardware security module, the digital certificate being previously simultaneously generated upon generation of the received cryptographic key pair; and
deriving a key-pair-specific transport key from a master transport key via a key-pair-specific derivation parameter which is generated once for every derived key-pair-specific transport key such that all derived key-pair-specific transport keys for different cryptographic key pairs differ among one another;
wherein the key-pair-specific transport key is utilized to decrypt the encrypted file.
8. The method as claimed in claim 7 , further comprising:
providing the digital certificate to a target device;
decrypting the encrypted file via the key-pair-specific transport key; and
providing the decrypted private key to the target device.
9. The method as claimed in claim 7 , further comprising:
providing the digital certificate to a target device;
providing the encrypted file to the target device; and
providing the key-pair-specific transport key to the target device.
10. The method as claimed in claim 7 , wherein the corresponding programmable hardware security module authenticates the target device.
11. The method as claimed in claim 8 , wherein the corresponding programmable hardware security module authenticates the target device.
12. The method as claimed in claim 9 , wherein the corresponding programmable hardware security module authenticates the target device.
13. The method as claimed in claim 7 , wherein the corresponding programmable hardware security module generates a target-device-specific key and provides one of (i) the private key and (ii) the key-pair-specific transport key to the target device in a manner protected utilizing the target-device-specific key.
14. The method as claimed in claim 6 , wherein the key-pair-specific transport key is derived via a key derivation function for which at least the key-pair-specific derivation parameter and the master transport key are prescribed as input parameters.
15. The method as claimed in claim 7 , wherein the key-pair-specific transport key is derived via a key derivation function for which at least the key-pair-specific derivation parameter and the master transport key are prescribed as input parameters.
16. The method as claimed in claim 6 , wherein the key-pair-specific derivation parameter is formed from certificate information of the digital certificate.
17. The method as claimed in claim 16 , wherein the certificate information of the digital certificate comprises one of (i) the public key, (ii) a device identifier and (iii) a hash value of the digital certificate.
18. The method as claimed in claim 7 , wherein the key-pair-specific derivation parameter is formed from certificate information of the digital certificate.
19. The method as claimed in claim 18 , wherein the certificate information of the digital certificate comprises one of (i) the public key, (ii) a device identifier and (iii) a hash value of the digital certificate.