Just a simple C# application that calculates the closest driver to a rider using Homomorphic Encryption.
see What Is Homomorphic Encryption? And Why Is It So Transformative?
This sample uses both C# Microsoft SEAL Library and Golang lattigo to perform the distance calculation under encryption:
On startup a Rider is assigned a random (x1, y1) coordinate in a 1000x1000 grid
Rider generates homomorphic publickey, secretkey: pk, sk
Rider encrypts the xy coordinates using pk:
pk(x1, y1) -> (x1', y1')Rider sends encrypted (x1', y1') and pk to server
Server sends pk to 50 drivers each in random positions in the grid.
Each driver encrypts their respective location using pk:
pk(x2, y2) -> (x2', y2')Each driver each sends (x2', y2') to the server
Server calculates over the still encrypted data the distance from the rider to each driver
d' = (x2'-x1')^2 + (y2'-y1')^2Server sends the encrypted result for each driver’s distance back to the rider
Rider decrypts distance from each driver using the sk:
sk(d') –> dRider picks the closest driver
The thing to note is the calculation done in step 8 is done using encrypted data….the server never decrypts any of the data its provided but nonetheless, it can calculate the distance value.
This repository also has a simple Apache Beam pipeline runner which will homomorphically add a given number to an already encrypted input. You can extend that sample to make further modifications and create a simple streaming ridesharing app.
You can find the source here
Use docker to build SEAL, compile the sample application and run:
The app will iterate over 50 random points, encrypt them and allow the Rider to decrypt the distance value:
docker build -t salrashid123/fhe .
docker run -t salrashid123/fhe
Rider at (281,399)
Driver at (137,340)
distance from rider: 24217
Driver at (949,705)
distance from rider: 539860
Driver at (730,973)
distance from rider: 531077
Driver at (41,178)
distance from rider: 106441
Driver at (212,203)
distance from rider: 43177
Driver at (429,30)
distance from rider: 158065
Driver at (446,821)
distance from rider: 205309
Driver at (690,224)
distance from rider: 197906
Driver at (488,105)
distance from rider: 129285
Driver at (832,112)
distance from rider: 385970
Driver at (199,64)
distance from rider: 118949
Driver at (347,400)
distance from rider: 4357 <<<<<<<<<<<<<
Driver at (804,181)
distance from rider: 321053
Driver at (1,123)
distance from rider: 154576
Driver at (520,514)
distance from rider: 70346
Driver at (346,862)
distance from rider: 218594
Driver at (962,107)
distance from rider: 549025
Driver at (23,634)
distance from rider: 121789
Driver at (808,673)
distance from rider: 352805
Driver at (389,597)
distance from rider: 50868
Cloest = 4357
The go program by itself does not run in a loop but rather individually processes each step as a command line. It’s trivial to change this to iterate all 50 within a loop automatically as in the C# sample but i just left it as a “standalone” command set.
The following runs each step as a standalone command set which is later wrapped into the runner.sh and iterate over 50 drivers:
## Create rider public,secret key
go run main.go -mode=genkey --pkFile=/tmp/rider/pk.bin --skFile=/tmp/rider/sk.bin
## Then test encryption/decryption for a rider at (x,y)=(2,2)
go run main.go -mode=encrypt --pkFile=/tmp/rider/pk.bin --x=2 --y=2 --encryptedFile=/tmp/rider/rider.bin
go run main.go -mode=decrypt --skFile=/tmp/rider/sk.bin --encryptedFile=/tmp/rider/rider.bin
## Use the riders public key to encrypt a drivers location at (4,5)
go run main.go -mode=encrypt --pkFile=/tmp/rider/pk.bin --x=4 --y=5 --encryptedFile=/tmp/drivers/1.bin
## Derive the distance between the rider and driver given their _encrypted_ values
go run main.go -mode=distance --riderEncryptedFile=/tmp/rider/rider.bin --driverEncryptedFile=/tmp/drivers/1.bin --encryptedFile=/tmp/distance/1.bin
## Rider decrypts each drivers' location
go run main.go -mode=decryptdistance --skFile=/tmp/rider/sk.bin --encryptedFile=/tmp/distance/1.bin
To run the above commands as a schell script,
./runner.sh
### RIder location and ID
2020/08/16 17:17:52 Decrypted: id: f1da6487-e005-11ea-baf5-e86a641d5560, (323,95)
## Driver location and ID
Driver [1] at (821, 145)
### Decrypted distance between driver and rider
2020/08/16 17:17:54 Distance: from Rider [f1da6487-e005-11ea-baf5-e86a641d5560] --> Driver [f26cc4e7-e005-11ea-bc51-e86a641d5560] (53893)
Driver [2] at (679, 726)
2020/08/16 17:17:56 Distance: from Rider [f1da6487-e005-11ea-baf5-e86a641d5560] --> Driver [f35334df-e005-11ea-b9be-e86a641d5560] (601) <<<<<
Driver [3] at (412, 800)
2020/08/16 17:17:57 Distance: from Rider [f1da6487-e005-11ea-baf5-e86a641d5560] --> Driver [f4517dc8-e005-11ea-add5-e86a641d5560] (46187)
Driver [4] at (180, 557)
2020/08/16 17:17:59 Distance: from Rider [f1da6487-e005-11ea-baf5-e86a641d5560] --> Driver [f53bb22b-e005-11ea-8e35-e86a641d5560] (37282)
Driver [5] at (438, 703)
2020/08/16 17:18:00 Distance: from Rider [f1da6487-e005-11ea-baf5-e86a641d5560] --> Driver [f629c73a-e005-11ea-8e46-e86a641d5560] (55204)
Driver [6] at (670, 888)
2020/08/16 17:18:02 Distance: from Rider [f1da6487-e005-11ea-baf5-e86a641d5560] --> Driver [f711526b-e005-11ea-b47f-e86a641d5560] (28351)
Driver [7] at (724, 574)
2020/08/16 17:18:03 Distance: from Rider [f1da6487-e005-11ea-baf5-e86a641d5560] --> Driver [f7e10d6c-e005-11ea-a901-e86a641d5560] (62557)
Driver [8] at (827, 107)
2020/08/16 17:18:05 Distance: from Rider [f1da6487-e005-11ea-baf5-e86a641d5560] --> Driver [f8bde225-e005-11ea-b0b7-e86a641d5560] (57549)
Driver [9] at (718, 975)
2020/08/16 17:18:06 Distance: from Rider [f1da6487-e005-11ea-baf5-e86a641d5560] --> Driver [f99c6359-e005-11ea-b50c-e86a641d5560] (12907)
Driver [10] at (886, 514)
2020/08/16 17:18:08 Distance: from Rider [f1da6487-e005-11ea-baf5-e86a641d5560] --> Driver [faa55930-e005-11ea-8d91-e86a641d5560] (33771)
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