Browse Prior Art Database

Efficient Rekeying (Key Rotation) of Encrypted Data Stored in a DSN Memory

IP.com Disclosure Number: IPCOM000248994D
Publication Date: 2017-Jan-25
Document File: 2 page(s) / 22K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is an efficient method for performing key rotation within a data source name (DSN) memory. The solution uses a linear error coding function and a linear encryption function to efficiently perform the key rotation entirely within each data source (ds) unit without having to gather and decode an Information Dispersal Algorithm (IDA) threshold number of slices and without having to re-error-code and store the slices.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

1

Efficient Rekeying (Key Rotation) of Encrypted Data Stored in a DSN Memory

For storage within a data source name (DSN) memory, data may be encrypted prior to being error coded and dispersed across a set of ds units. Best practices and policies often dictate that, from time to time, the encryption key used to encrypt data be changed. This action is known as re-keying or "key rotation". Key rotation involves:

1. Reading the stored encrypted data 2. Decrypting the original data with the old encryption key 3. Generating a new encryption key 4. Re-encrypting the decrypted data with the new encryption key 5. Storing the re-encrypted data

This is an expensive operation, especially within a DSN memory, because at least a read threshold number of slices needs to be recombined to recover the original encrypted data before performing the second step. The data requires re-error coding and restoring to at least a write threshold number of ds units.

However, certain error coding functions have a property known as linearity. This is the property wherein a function F has the property that F(A + B) = F(A) + F(B) -- note addition here may be in a field, such as GaloisField(2^p) wherein addition is defined as the bit-wise exclusive or operation. This same property of linearity exists for a class of encryption functions such as stream ciphers or block ciphers operating in certain modes such as CTR (counter), OFB (output feedback), CFB (cipher feedback) modes.

The novel solution is to use a linear error coding function and a linear encryption function to efficiently perform the key rotation entirely within each ds unit without having to gather and decode an Information Dispersal Algorithm (IDA) threshold number of slices and without having to re-error-code and store the slices.

To perform this efficient re-keying operation: 1. The old encryption key (K1) and the new encryption key (K2) are sent to each of

the ds units 2. Both K1 and K2 are used to generate key-streams (S1) and (S2), respectively, of

length equal to the original data source for the slice each holds...