1. Searchable Encryption
陳榮傑
交通大學資工系
Cryptanalysis Lab
2012/03/29

2. Searchable Encryption
kw : keyword
Encrypt:
Encrypted data
PEKS(kw)s
Alice
Search kw:
Trapdoor(kw’)
Test:
for each file
tests PEKS
(using pairing-based cryptography)
Reply:
Encrypted files which contains kw’
Server gains no knowledge about kw or the file content stored on the Cloud Storage

3. Searchable Encryption
kw : keyword
Encrypt:
Encrypted data
PEKS(kw)s A B C
Alice
Search kw:
Trapdoor(kw’) C
Test:
for each file
tests PEKS
(using pairing-based cryptography)
Test:
for each file
tests PEKS
Reply:
Encrypted files which contains kw’
Server gains no knowledge about kw or the file content stored on the Cloud Storage

4. Data
Example

5. Data
Example
Keyword Lists (311.tags)

6. Public Key Encryption with Keyword Search (PEKS) (1/3)
311.pdf
311.pdf
311.tags
Keyword
Encryption
ECIES key
311.cipher
PEKS INDEX

7. Search Keyword Search kw: Trapdoor(author: Brent Waters,
Alice’s private key)
Alice
Test:
for each file
tests PEKS in
Reply:
Encrypted files which contains kw
PEKS INDEX
311.aes128
311.rsa

8. Search Keyword File 1: PEKS(id) PEKS(title) PEKS(author1)⁞
File 2:
PEKS(author)
PEKS(keyword1)
PEKS(keyword2)
Trapdoor(author: Brent Waters)
PEKS INDEX
Trapdoor(author: Brent Waters)
𝑃𝐸𝐾𝑆= 𝑔 𝑟 , 𝐻 2 𝑡 , 𝑡=𝑒 𝐻 1 𝐾𝑊 , ℎ 𝑟 , ℎ= 𝑔 𝛼
𝑇𝑟𝑎𝑝𝑑𝑜𝑜𝑟= 𝐻 1 𝐾𝑊 𝛼
𝑆𝑒𝑟𝑣𝑒𝑟 𝑡𝑒𝑠𝑡𝑠 𝑒𝑎𝑐ℎ 𝑃𝐸𝐾𝑆 𝑤ℎ𝑒𝑡ℎ𝑒𝑟 𝐻 2 𝑒( 𝐻 1 𝐾𝑊 𝛼 , 𝑔 𝑟 = 𝐻 2 𝑡

9. Implementation PBC Library by Ben Lynn Tate Pairing
supersingular curve: y2 = x3 + x over Fq
embedding degree k = 2
q is a prime and q ≡ 3 mod 4
q is 1536-bit long
group order r is 256-bit long
Key Length:

10. Forthcoming Research
To enhance search capability

11. Demo PEKS library

12. Questions?
Thank you