# US 8,787,583 B2 · Systems and methods for distributing and securing data

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- Number: US 8,787,583 B2
- Document ID: US8787583B2
- Status: Granted
- Kind: B2
- Application number: 13/412,111
- Filed: 2012-03-05
- Published: 2012-06-28
- Granted: 2014-07-22
- Earliest claimed: 2006-11-07
- Assignees: Security First Corp.
- Applicants: Mihir Bellare; Phillip Rogaway
- Inventors: Mihir Bellare; Phillip Rogaway
- Web page: https://patentgrep.com/patent/US8787583B2

## CPC

- H04L 9/0894: {Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage}
- H04L 9/0816: {Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use}
- H04L 9/085: {Secret sharing or secret splitting, e.g. threshold schemes}
- H04L 9/14: using a plurality of keys or algorithms
- H04L 9/321: {involving a third party or a trusted authority}
- H04L 9/3218: {using proof of knowledge, e.g. Fiat-Shamir, GQ, Schnorr, ornon-interactive zero-knowledge proofs}
- H04L 9/3231: {Biological data, e.g. fingerprint, voice or retina (network architectures or network communication protocols for supporting authentication of entities using biometrical features in a packet data network H04L63/0861)}
- G06F 21/64: Protecting data integrity, e.g. using checksums, certificates or signatures
- H04L 2209/24: Key scheduling, i.e. generating round keys or sub-keys for block encryption
- H04L 2209/56: Financial cryptography, e.g. electronic payment or e-cash
- H04L 2209/805: Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

A robust computational secret sharing scheme that provides for the efficient distribution and subsequent recovery of a private data is disclosed. A cryptographic key may be randomly generated and then shared using a secret sharing algorithm to generate a collection of key shares. The private data may be encrypted using the key, resulting in a ciphertext. The ciphertext may then be broken into ciphertext fragments using an Information Dispersal Algorithm. Each key share and a corresponding ciphertext fragment are provided as input to a committal method of a probabilistic commitment scheme, resulting in a committal value and a decommittal value. The share for the robust computational secret sharing scheme may be obtained by combining the key share, the ciphertext fragment, the decommittal value, and the vector of committal values.

## Claims

### Claim 1

A method for securing data by generating a collection of fragments from the data, the method comprising:
applying by a hardware processor a sharing mechanism of a computational secret sharing scheme to the data to produce a collection of shares;
generating a random or pseudo-random value;
computing a set of committal values and a set of decommittal values from the random or pseudo-random value and the collection of shares;
producing each fragment in the collection of fragments by combining a share, a decommittal value, and at least two committal values of the set of committal values; and
storing each fragment on at least one data repository.

### Claim 2 (depends on 1)

The method of claim 1 where in producing each fragment in the collection of fragments comprises combining a share, a decommittal value, and the entire set of committal values.

### Claim 3 (depends on 1)

The method of claim 1 wherein storing each fragment on at least one data repository comprises storing each fragment at different geographic locations.

### Claim 4 (depends on 1)

The method of claim 1 wherein storing each fragment on at least one data repository comprises storing each fragment at different physical locations on the at least one data repository.

### Claim 5 (depends on 1)

The method of claim 1 wherein the at least one data repository comprises a distributed file system.

### Claim 6 (depends on 1)

The method of claim 1 wherein the computational secret sharing scheme is selected from the group consisting of the Shamir, Blakley, and Krawczyk secret sharing schemes.

### Claim 7 (depends on 1)

The method of claim 1 wherein computing a set of committal values and a set of decommittal values comprises employing a probabilistic commitment scheme.

### Claim 8 (depends on 1)

The method of claim 1 further comprising transmitting the produced fragments over a plurality of communication channels.

### Claim 9 (depends on 8)

The method of claim 8 wherein transmitting the produced fragments over a plurality of communication channels comprises transmitting each produced fragment over a different communication channel.

### Claim 10

A method for securing data, the method comprising:
applying by a hardware processor a sharing mechanism of a computational secret sharing scheme to the data to produce a collection of shares;
using a probabilistic commitment scheme to compute a set of committal values and a set of decommittal values from the collection of shares;
producing a plurality of fragments, wherein each fragment comprises a share of the collection of shares, a decommittal value of the set of decommittal values, and at least two committal values of the set of committal values; and
storing each fragment on at least one data repository.

### Claim 11 (depends on 10)

The method of claim 10 wherein storing each fragment on at least one data repository comprises storing each fragment at different geographic locations.

### Claim 12 (depends on 10)

The method of claim 10 wherein storing each fragment on at least one data repository comprises storing each fragment at different physical locations on the at least one data repository.

### Claim 13 (depends on 10)

The method of claim 10 wherein the at least one data repository comprises a distributed file system.

### Claim 14 (depends on 10)

The method of claim 10 wherein the computational secret sharing scheme is selected from the group consisting of the Shamir, Blakley, and Krawczyk secret sharing schemes.

### Claim 15 (depends on 10)

The method of claim 10 further comprising transmitting the produced fragments over a plurality of communication channels.

### Claim 16 (depends on 15)

The method of claim 15 wherein transmitting the produced fragments over a plurality of communication channels comprises transmitting each produced fragment over a different communication channel.

### Claim 17

A method for securing data comprising;
generating a cryptographic key;
encrypting by a hardware processor the data with the cryptographic key to create a ciphertext;
producing a collection of key shares by applying a secret sharing scheme to the cryptographic key;
producing a collection of ciphertext chunks by applying an information dispersal algorithm to the ciphertext;
computing n committal values and a set of decommittal values by applying a probabilistic commitment scheme to each of the key shares and ciphertext chunks, where n is an integer equal to or greater than two;
producing a collection of data fragments, wherein each data fragment is a function of a key share, a ciphertext chunk, a decommittal value, and at least two committal values of the n committal values; and
storing the data fragments on different logical storage devices, whereby the data is recoverable from a predefined number of the data fragments.

### Claim 18 (depends on 17)

The method of claim 17 wherein storing the data fragments on different logical storage devices comprises storing the data fragments on different logical storage devices.

### Claim 19 (depends on 17)

The method of claim 17 further comprising transmitting the data fragments over communication channels before storing the data fragments.