Enabling comparable data access control for lightweight mobile devices in clouds

• US 10,419,404 B2
• Filed: 06/08/2017
• Issued: 09/17/2019
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Arizona Board of Regents (University of Arizona)
• Original Assignee: Arizona Board of Regents (University of Arizona)
• Inventors: Huang, Dijiang, Wang, Zhijie
• Primary Examiner(s): Choudhury, Azizul
• Application Number:
  US15/617,035
• Publication Number:
  US 20170272411A1
• Time in Patent Office: 831 Days
• CPC Class Codes: G06F 21/6218 to a system of files or objects, e.g. local or distributed file system or database
• CPC Class Codes: H04L 2209/805 Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04L 63/06 for supporting key management in a packet data network cryptographic mechanisms or cryptographic arrangements for key management H04L9/08
• CPC Class Codes: H04L 63/102 Entity profiles
• CPC Class Codes: H04L 9/3073 involving pairings, e.g. identity based encryption [IBE], bilinear mappings or bilinear pairings, e.g. Weil or Tate pairing

Abstract

A new efficient framework based on a Constant-size Ciphertext Policy Comparative Attribute-Based Encryption (CCP-CABE) approach. CCP-CABE assists lightweight mobile devices and storing privacy-sensitive sensitive data into cloudbased storage by offloading major cryptography-computation overhead into the cloud without exposing data content to the cloud. CCP-CABE extends existing attribute-based data access control solutions by incorporating comparable attributes to incorporate more flexible security access control policies. CCP-CABE generates constant-size ciphertext regardless of the number of involved attributes, which is suitable for mobile devices considering their limited communication and storage capacities.

Claims

1. A method for encrypting data in a computer based processing system using a trust authority with a public key PK and a master key MK, the method comprising:

sending a request for a partially encrypted header {tilde over (H)} to the trust authority with a specified access control policy Ps;

receiving a partially encrypted header computed by the trust authority, wherein the partially encrypted header {tilde over (H)} is based on the public key PK, the master key MK, and the specified access control policy Ps;

encrypting data using the partially encrypted header {tilde over (H)};

wherein the data is encrypted according to the following algorithm;

Encrypt(Ĥ

)→

(H, K_s);

Given the partially encrypted header, the algorithm produces the session key K_s and ciphertext H={_S, C, E_S, E_S, Ê

_S, Ê

_S} to cloud storage; and

further wherein each part of H is generated as follows;

1) randomly choosing two secrets s₁, s₂ ∈

_n,

2) computing the main secret s=s₁+s₂ ∈

_n and deriving

C=sW∈

,

3) producing the session key K_s=e(G, W)<sup>α

s</sup> and using K_s to encrypt the data,

4) computing E_S=s₁T and E_S=s₂T, and

5) computing each of Ê

_S=s₁{right arrow over (ψ

)}_ST·

s₁W=s₁{right arrow over (ψ

)}_Sλ

W·

s₁W=s₁(λ

{right arrow over (ψ

)}_S+1)W and Ê

_S=s_2ST·

s₂W=s_2Sλ

W·

s₂W=s₂(λ

_S+1)W.

2. The method of claim 1, wherein the step of encrypting the data comprises generating the session key K_s and the ciphertext H using the partially encrypted header {tilde over (H)}.

3. The method of claim 1, wherein the computer based processing system is a cloud storage system.

4. The method of claim 1, wherein the size of any key and any ciphertext overhead remains constant without regard to a number of attributes.

5. The method of claim 1, wherein the algorithm term

H={_S, C, E_S, E_S, Ê

_S, Ê

_S} represents ciphertext H being generated as a function of;

C, the product of the main secret s (the sum of two random secrets s₁ and s₂) and generator W, which are elements of set ;

E_S, the product of secret 1 (s₁) and T=λ

W∈

, the product of λ and

generator W, elements of set ;

E_S, the product of secret 2 (s₂) and T=λ

W∈

, the product of λ and

generator W, elements of set ;

Ê

_Sthe function of secret 1 (s₁), λ

(an element of the master key), {right arrow over (ψ

)}_S(the first part of the partially decrypted header) and generator W; and

Ê

_S, the function of secret 2 (s₂), λ

(an element of the master key), _S(the second part of the partially decrypted header) and generator W.

6. A method of decrypting data, wherein the method comprises:

storing the data in a computer based processing system, wherein the data includes an encrypted header H and encrypted target data;

receiving a request for access to the data, wherein the request includes a user identity;

partially decrypting an encrypted header H when the user is entitled to access the data based on the user'"'"'s public key PKLU, privilege LU and access control policy Ps;

sending the partially decrypted header {tilde over (H)} to the user;

wherein partially decrypting the header H is performed according to the following algorithm;

DecDelegate(H, PK_u, _u, _S)→

Ĥ

;

Given the user'"'"'s public key PK_u and privilege _u along with the access control policy _s, the algorithm outputs {right arrow over (ψ

)}_Sand _Swhen [ν

_i,j, ν

_i,k]∩

[ν

_i,a, ν

_i,b]≠

Ø

for all A_i∈

;

({right arrow over (ψ

)}_U)=({right arrow over (ψ

)}_U)^wU,s=({right arrow over (π

)}<sup>Π

1≤

i≤

m{right arrow over (w)}i,a</sup>)<sup>Π

1≤

i≤

m(wi,(a,k))</sup>={right arrow over (ψ

)}_S(mod n)

(_Ū

)=(_Ū

)^ws,Ū

=(<sup>Π

1≤

i≤

mi,b</sup>)<sup>Π

1≤

i≤

m(wi,(j,b))</sup>=_s(mod n);

where {right arrow over (w)}_U,s=Π

<sub>1≤

i≤

m</sub>(w_i,(a,k)) and w_S,Ū

=Π

<sub>1≤

i≤

m</sub>(w_i,(j,b));

and further wherein the algorithm outputs {tilde over (H)}={H,{right arrow over (ψ

)}_U−

{right arrow over (ψ

)}_S, _Ū

−

_S} as the partially decrypted header.

7. The method of claim 6, further comprising:

retrieving a session key K_s;

Decrypt(, Ĥ

)→

K_S;

Given the delegation key and header Ĥ

, the algorithm performs the following computation;

8. The method of claim 7, further comprising decrypting data utilizing the session key K_s.

9. The method of claim 8, wherein the processing system comprises a cloud storage system.

10. The method of claim 6, wherein the access control policy Ps is revealed at an attribute domain level.

11. The method of claim 6, wherein encryption of the header H and the partially decrypting of the encrypted header H are performed over each of a plurality of attribute domains in a batch-processing manner.

12. The method of claim 6, wherein the algorithm terms

({right arrow over (ψ

)}_U)=({right arrow over (ψ

)}_U)^wU,s=({right arrow over (π

)}<sup>Π

1≤

i≤

m{right arrow over (w)}i,a</sup>)<sup>Π

1≤

i≤

m(wi,(a,k))</sup>={right arrow over (ψ

)}_S(mod n);

(_Ū

)=(_Ū

)^wS,Ū

=(<sup>Π

1≤

i≤

mi,b</sup>)<sup>Π

1≤

i≤

m(wi,(j,b))</sup>=_s(mod n); and

{tilde over (H)}={H,{right arrow over (ψ

)}_U−

{right arrow over (ψ

)}_S,_Ū

−

_S}only if [ν

_i,j, ν

_i,k]∩

[ν

_i,a, ν

_i,b]≠

Ø

for all A_i∈

represent the first and second parts of the partially decrypted header {right arrow over (ψ

)}_Sand _S, respectively, as outputted when the user'"'"'s attribute range (A_i) on the i-th attribute of the attribute set [ν

_i,a, ν

_i,b] matches the access control policy'"'"'s attribute range on attribute A_i [ν

_i,j, ν

_i,k]; and

wherein the partially decrypted header is outputted as a function of encrypted header H, the difference beween the first part of the public key {right arrow over (ψ

)}_Uand partially decrypted header {right arrow over (ψ

)}_Sand the difference between the second part of the public key _Ū

and the second part of the partially decrypted header _S.