STORING AND RETRIEVING CIPHERTEXT IN DATA STORAGE

• US 20160344553A1
• Filed: 04/04/2014
• Published: 11/24/2016
• Est. Priority Date: 04/04/2014
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Camble, Peter T., Bucklngham, Jonathan P., Radon, Hendrik, Chen, Liqun, Pelly, Simon, Shiu, Simon Kai-Ying, Ficara, Joseph S.
• Granted Patent: US 10,374,807 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1453 using de-duplication of the data
• CPC Class Codes: G06F 16/2365 Ensuring data consistency and integrity
• CPC Class Codes: G06F 16/278 Data partitioning, e.g. horizontal or vertical partitioning
• CPC Class Codes: G06F 21/602 Providing cryptographic facilities or services
• CPC Class Codes: G06F 21/79 in semiconductor storage media, e.g. directly-addressable memories
• CPC Class Codes: G06F 2201/83 the solution involving signatures
• CPC Class Codes: G06F 2221/2107 File encryption
• 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 9/3242 involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC

Abstract

Storing and retrieving ciphertext in data storage can include determining a first ciphertext value for a first data chunk to be saved to a client-server data storage system using an encrypted chunk hash value associated with the first data chunk as an initial value, and storing the first data chunk on a server in the client-server data storage system in response to determining that the first ciphertext value is a unique ciphertext value. Also, storing and retrieving ciphertext in data storage can include decrypting a ciphertext value for a second data chunk received from a client in the client-server data storage system and based on an encrypted chunk hash value associated with the second data chunk, and sending the second data chunk to the client in response to determining that the decrypted ciphertext value corresponds to an original data chunk saved to the server by the client.

Claims

1. A system, comprising:

a data storage engine to;

determine a first ciphertext value for a first data chunk to be saved to a client-server data storage system using, as an initial value for encryption, an encrypted chunk hash value associated with the first data chunk; and

provide the first ciphertext value to a server in the client-server data storage system for storage, when the encrypted chunk hash value associated with the first data chunk is not stored in an index of the server; and

a data retrieval engine to;

decrypt a second ciphertext value for a second data chunk, requested from the server by a client in the client-server data storage system, the decryption using an encrypted chunk hash value associated with the second data chunk; and

determine that the decrypted second ciphertext value corresponds to the requested second data chunk.

2. The system of claim 1, wherein the data storage engine is further to determine the first ciphertext value using a concatenation of a second ciphertext value for the first data chunk and a message authentication code (MAC) value for the first data chunk.

3. The system of claim 1, wherein, to determine that the decrypted second ciphertext value corresponds to the requested second data chunk, the data retrieval engine is to determine that a hash of the decrypted second ciphertext value is the same as a decryption value determined using the encrypted chunk hash value.

4. The system of claim 1, wherein the data retrieval engine is to determine a first message authentication code (MAC) value for the second data chunk using an encryption key for a MAC operation and a concatenation of the encrypted chunk hash for the second data chunk and the second ciphertext value for the second data chunk.

5. The system of claim 4, wherein to determine that the decrypted second ciphertext value corresponds to the requested second data chunk, the data retrieval engine is to determine whether the first MAC value is the same as a second MAC value determined based on the requested second data chunk.

8. The system of claim 1, wherein, in response to receiving the client request for the second data chunk, the server in the client-server data storage system is to identify, from a deduplication index, the encrypted chunk hash value associated with the second data chunk.

9. The system of claim 1, wherein, in response to receiving the client request for the second data chunk, the server in the client-server data storage system is to identify the second ciphertext value associated with the data chunk from a list of encrypted data chunks, and return the identified second ciphertext value to the client.

6. A non-transitory computer readable medium storing instructions executable by a processing resource to cause a computer to:

calculate a first decryption value for a data chunk in a client-server data storage system using an encryption key, an encrypted chunk hash value as an initial value for decryption, and ciphertext associated with the data chunk;

calculate a second decryption value using the encryption key and the encrypted chunk hash value;

calculate a hash value of the first decryption value; and

determine whether to accept or reject the first decryption value as equivalent to the data chunk, based on the calculated hash value and the second decryption value.

7. The non-transitory computer readable medium of claim 6, including instructions executable to calculate a respective first decryption value for each of a plurality of data chunks in a data stream in the client-server data storage system.

10. A method, comprising:

for each of a number of chunks in a data stream in a client-server data storage system, computing a hash value of the chunk and an encrypted chunk hash value from the hash value;

creating a manifest of the data stream, wherein the manifest includes an ordered list of the encrypted chunk hash values for the number of chunks; and

for a particular encrypted chunk hash value in the manifest that is not included in an index maintained by the server, computing, with a data storage engine of a client, a first ciphertext value for a particular data chunk, of the number of data chunks, for which the particular encrypted chunk hash value was computed, wherein computing the first ciphertext value comprises using the particular encrypted chunk hash value as an initial value for encryption.

11. The method of claim 10, wherein the first ciphertext value is computed as a function of an encryption key, the particular encrypted chunk hash value, and plaintext of the particular data chunk.

12. The method of claim 10, wherein the first ciphertext value is determined using an encrypt-then-message authentication code (MAC) model.

13. The method of claim 12, wherein the encrypt-then-MAC model includes:

computing a second ciphertext value as a function of an encryption key for an encryption function, the particular encrypted chunk hash value, and plaintext of the particular data chunk;

computing a MAC value as a function of an encryption key for a MAC function and a concatenation of the particular encrypted chunk hash value and the second ciphertext value; and

computing the first ciphertext value as a concatenation of the second ciphertext value and the MAC value.

14. The method of claim 13, wherein computing the MAC value is performed using a keyed-hash message authentication code model.

15. The method of claim 10, wherein computing the first ciphertext value is performed using a xor-encrypt-xor based tweaked-codebook mode with ciphertext stealing advanced encryption standard model.