vineet-garg/assignment-2

Limits:

1. Input can be a signed 32 bit integer.
2. Number of requests can be 2^63 - 1 as count is a long data type
3. Key is provided through a file based configuration file. Needs to be protected through host hardening.
4. Algorithm and Algorithm parameters are hardcoded, but can be made configurable to facilitate quick transition to any other algorithm.
5. System supports only one key. APIs are designed to accomodate possible future requirements like: key rotation, re-keying, crypto agility.
6. Server supports http connection only.
7. Encrypt/Decrypt functionality is not access controlled or rate limited.

Choices:

Encryption parameters are as per NIST recommendations (NIST SP-800 38D). The data size is small: 32 bit Float, the size of overhead (extra bits for IV and authentication Tag) is kept small too balancing between bandwith and security. Access controlling, rate limiting and monitoring Encryption service along with a key roation policy can mitigate the security loss due to small values of IV and authentication Tag. They are in general nice for a production-use service. A comprehensive threat modelling of the feature, identifying sensitivity level of data being protected will enable making more informed choices.

1. Key used is AES-256 bit.
2. Encryption mode used is GCM/NoPadding.
3. CBC/PKCSPadding was considered as well but as Decrypt is not access controlled or rate limited, it would be vulnerable to padding ORACLE attack.
4. IV size is 96 bit
5. Authentication tag size is 96 bit
6. IV is returned in plain along with Encrypted data, with GCM this is considered safe (unlike in CBC mode which is prone to clear IV attacks).
7. Encryption and decryption errors are not propagated to the clients, this can be usability tradeoff.

References:

Standard deviation calculation:

• Welford's online algorithm on wikipedia.

Encryption:

• AES-GCM: NIST SP-800 38D.

Steps:

1. Install JDK (jdk-17.0.1) and maven (Apache Maven 3.8.4), set $JAVA_HOME

   export JAVA_HOME=<Path to jdk's parent folder>/jdk-17.0.1

2. Clone The repo

  mkdir -p $HOME/test
  cd $HOME/test
  git clone https://github.com/vineet-garg/assignment-2.git
  cd assignment-2

3. Build

mvn clean

mvn test

   .......
	at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:85)
	at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:115)
	at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:75)
Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.021 sec
Running crypto.webservice.services.StatsSvcImplTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.004 sec

Results :

Tests run: 9, Failures: 0, Errors: 0, Skipped: 0

mvn package

4. Start the server (server properties like port numbers can be changed in server.yaml file, default are 8080 and 8081)

$JAVA_HOME/bin/java -jar $HOME/test/assignment-2/target/crypto.webservice-0.0.1-SNAPSHOT.jar server server.yaml

5. Sample APIs invocations using curl commands

curl -H "Accept: application/json" -H "Content-type: application/json" -X POST -d '{"num":2}'  http://0.0.0.0:8080/push-and-recalculate

{"avg":{"num":10.0},"sd":{"num":10.0}}

curl -H "Accept: application/json" -H "Content-type: application/json" -X POST -d '{"num":20}'  http://0.0.0.0:8080/push-recalculate-and-encrypt

{"avg":{"cipherTxt":"AhDjGm/TwOar80AcickyZfAICokOwTPwTqbJZA==","keyId":"0"},"sd":{"cipherTxt":"5EOD9kTkti7XtTN2q6uhVHnQyYDsC1lAaLhNyg==","keyId":"0"}}

curl -H "Accept: application/json" -H "Content-type: application/json" -X POST -d '{"cipherTxt":"AhDjGm/TwOar80AcickyZfAICokOwTPwTqbJZA==","keyId":"0"}'  http://0.0.0.0:8080/decrypt

{"num":13.333333}

curl -H "Accept: application/json" -H "Content-type: application/json" -X POST -d '{"cipherTxt":"5EOD9kTkti7XtTN2q6uhVHnQyYDsC1lAaLhNyg==","keyId":"0"}'  http://0.0.0.0:8080/decrypt

{"num":9.428091}