Decrypting encrypted data on an electronic device

• US 10,341,102 B2
• Filed: 09/02/2016
• Issued: 07/02/2019
• Est. Priority Date: 09/02/2016
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Bowman, Roger Paul, Pechkin, Dmitri
• Primary Examiner(s): Holder, Bradley W
• Application Number:
  US15/255,960
• Publication Number:
  US 20180069699A1
• Time in Patent Office: 1,033 Days
• CPC Class Codes: H04L 9/002 Countermeasures against attacks on cryptographic mechanisms network architectures or network communication protocols for protection against malicious traffic H04L63/1441
• CPC Class Codes: H04L 9/006 involving public key infrastructure [PKI] trust models network architecture or network communication protocol for supporting authentication of entities using certificates in a packet data network H04L63/0823
• CPC Class Codes: H04L 9/0631 Substitution permutation network [SPN], i.e. cipher composed of a number of stages or rounds each involving linear and nonlinear transformations, e.g. AES algorithms
• CPC Class Codes: H04L 9/0643 Hash functions, e.g. MD5, SHA, HMAC or f9 MAC
• CPC Class Codes: H04L 9/0822 using key encryption key
• CPC Class Codes: H04L 9/0841 involving Diffie-Hellman or related key agreement protocols
• CPC Class Codes: H04L 9/0861 Generation of secret information including derivation or calculation of cryptographic keys or passwords
• CPC Class Codes: H04L 9/0894 Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage
• CPC Class Codes: H04L 9/14 using a plurality of keys or algorithms
• CPC Class Codes: H04L 9/3066 involving algebraic varieties, e.g. elliptic or hyper-elliptic curves

Abstract

Systems, methods, and software can be used to encrypt and decrypt data. In some aspects, a decryption request to decrypt the encrypted data is received from an application on an electronic device. A first secret key from a shared secret is generated. The shared secret is generated based on a master private key and an ephemeral public key associated with the encrypted data. A first encrypted secret key is generated using the first secret key and a context key. The context key is generated based on the master private key. A first portion of the encrypted data is decrypted using the first secret key. A second secret key is generated from the first secret key. The first secret key is deleted. At least a segment of the decrypted first portion of the encrypted data is sent to the application.

Claims

1. A method of decrypting encrypted data, the method comprising:

receiving, from an application on an electronic device, a decryption request to decrypt the encrypted data;

generating, by a hardware processor of the electronic device, a first secret key from a shared secret, wherein the shared secret is generated based on a master private key and an ephemeral public key associated with the encrypted data;

encrypting, by the hardware processor of the electronic device, the first secret key to generate a first encrypted secret key by using a context key, wherein the context key is generated based on the master private key;

decrypting a first portion of the encrypted data using the first secret key;

generating a second secret key from the first secret key;

deleting the first secret key;

decrypting a second portion of the encrypted data using the second secret key;

deleting the second secret key;

deleting the first encrypted secret key; and

sending at least a segment of the decrypted first portion of the encrypted data and at least a segment of the decrypted second portion of the encrypted data to the application.

2. The method of claim 1, wherein the first secret key is generated from the shared secret using a key derivation function, and the second secret key is generated from the first secret key using the key derivation function.

3. The method of claim 1, further comprising:

prior to deleting the second secret key, generating a third secret key from the second secret key.

4. The method of claim 1, further comprising:

detecting a lock event; and

in response to detecting the lock event, deleting the context key and the master private key.

5. The method of claim 1, further comprising:

detecting an unlock event while in a locked state;

determing a current portion of the encrypted data for decrypting;

retrieving a current encrypted secret key;

generating, by the hardware processor, the context key based on the master private key;

generating, by the hardware processor, a current secret key by decrypting the current encrypted secret key using the context key; and

decrypting the current portion of the encrypted data using the current secret key.

6. The method of claim 1, wherein the decryption request indicates one or more segements in the encrypted data to be decrypted, and the method further comprising storing a last encrypted secret key that is used to decrypt a last segment of one or more segments indicated in the decryption request.

7. The method of claim 6, further comprising:

receiving a second decryption request, wherein the second decryption request indicates a different segment in the encrypted data to be decrypted;

generating, by the hardware processor, the context key based on the master private key;

generating, by the hardware processor, a last secret key by decrypting the last encrypted secret key using the context key; and

decrypting the different segment using the last secret key.

8. An electronic device, comprising:

a memory; and

at least one hardware processor communicatively coupled with the memory and configured to;

receive, from an application on the electronic device, a decryption request to decrypt encrypted data;

generate a first secret key from a shared secret, wherein the shared secret is generated based on a master private key and an ephemeral public key associated with the encrypted data;

encrypt, the first secret key to generate a first encrypted secret key by using a context key, wherein the context key is generated based on the master private key;

decrypt a first portion of the encrypted data using the first secret key;

generate a second secret key from the first secret key;

delete the first secret key;

decrypt a second portion of the encrypted data using the second secret key;

delete the second secret key;

delete the first encrypted secret key; and

send at least a segment of the decrypted first portion of the encrypted data and at least a segment of the decrypted second portion of the encrypted data to the application.

9. The electronic device of claim 8, wherein the first secret key is generated from the shared secret using a key derivation function, and the second secret key is generated from the first secret key using the key derivation function.

10. The electronic device of claim 8, wherein the at least one hardware processor is further configured to:

prior to deleting the second secret key, generate a third secret key from the second secret key.

11. The electronic device of claim 8, wherein the at least one hardware processor is further configured to:

detect a lock event; and

in response to detecting the lock event, delete the context key and the master private key.

12. The electronic device of claim 8, wherein the at least one hardware processor is further configured to:

detect an unlock event while in a locked state;

determine a current portion of the encrypted data for decrypting;

retrieve a current encrypted secret key;

generate the context key based on the master private key;

generate a current secret key by decrypting the current encrypted secret key using the context key; and

decrypt the current portion of the encrypted data using the current secret key.

13. The electronic device of claim 8, wherein the decryption request indicates one or more segements in the encrypted data to be decrypted, and the at least one hardware processor is further configured to store a last encrypted secret key that is used to decrypt a last segment of one or more segments indicated in the decryption request.

14. The electronic device of claim 13, wherein the at least one hardware processor is further configured to:

receive a second decryption request, wherein the second decryption request indicates a different segment in the encrypted data to be decrypted;

generate the context key based on the master private key;

generate a last secret key by decrypting the last encrypted secret key using the context key; and

decrypt the different segment using the last secret key.

15. A non-transitory computer-readable medium containing instructions which, when executed, cause an electronic device to perform operations comprising:

receiving, from an application on the electronic device, a decryption request to decrypt encrypted data;

generating, by a hardware processor of the electronic device, a first secret key from a shared secret, wherein the shared secret is generated based on a master private key and an ephemeral public key associated with the encrypted data;

encrypting, by the hardware processor of the electronic device, the first secret key to generate a first encrypted secret key by using a context key, wherein the context key is generated based on the master private key;

decrypting a first portion of the encrypted data using the first secret key;

generating a second secret key from the first secret key;

deleting the first secret key;

decrypting a second portion of the encrypted data using the second secret key;

deleting the second secret key;

deleting the first encrypted secret key; and

sending at least a segment of the decrypted first portion of the encrypted data and at least a segment of the decrypted second portion of the encrypted data to the application.

16. The non-transitory computer-readable medium of claim 15, wherein the first secret key is generated from the shared secret using a key derivation function, and the second secret key is generated from the first secret key using the key derivation function.

17. The non-transitory computer-readable medium of claim 15, the operations further comprising:

prior to deleting the second secret key, generating a third secret key from the second secret key.

18. The non-transitory computer-readable medium of claim 15, the operations further comprising:

detecting a lock event; and

in response to detecting the lock event, deleting the context key and the master private key.

19. The non-transitory computer-readable medium of claim 15, the operations further comprising:

detecting an unlock event while in a locked state;

determing a current portion of the encrypted data for decrypting;

retrieving a current encrypted secret key;

generating, by the hardware processor, the context key based on the master private key;

generating, by the hardware processor, a current secret key by decrypting the current encrypted secret key using the context key; and

decrypting the current portion of the encrypted data using the current secret key.

20. The non-transitory computer-readable medium of claim 15, wherein the decryption request indicates one or more segements in the encrypted data to be decrypted, and the operations further comprising storing a last encrypted secret key that is used to decrypt a last segment of one or more segments indicated in the decryption request.