3AgxLqQE

1public class KeyGenerationHandler {
2    private final HashMap<String,GeneratedKey> keyMap = new HashMap<>();
3    private final Object lock = new Object();
4
5    private byte[] createKey() throws java.security.NoSuchAlgorithmException{
6        final KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
7        keyGenerator.init(256);
8        final SecretKey key = keyGenerator.generateKey();
9        return key.getEncoded();
10    }
11
12    public byte[] getKey(String userId, String partnerId) throws java.security.NoSuchAlgorithmException {
13
14        String existingSessionId = partnerId + userId;
15
16        synchronized (lock){
17            if(keyMap.containsKey(existingSessionId)){
18                return keyMap.remove(existingSessionId).keyBytes;
19            }else{
20                String newSessionId = userId + partnerId;
21                byte[] newKey = createKey();
22                GeneratedKey generatedKey = new GeneratedKey(newKey);
23                keyMap.put(newSessionId,generatedKey);
24                return newKey;
25            }
26        }
27    }
28}