CRYPTO

Admes Cryptography Algorithms Guide.

Used methods:
- AES-ECB 128bit (192bit and 256 bit are released,
  but not used);
- AES-CBC 128bit (192bit and 256 bit are released,
  but not used);
- Encryption/Decryption based on ellipric curve cryptography;
- Making/Checking signature based on ellipric curve cryptography;
- PRNGa based on ellipric curve cryptography;
- PRNGb based on time of typing.

PRNGa Algorithm:

Input: elliptic curve parameters, where G is group generator, seed.
Output: pseudo-random number

1. Q = seed*G
2. seed := Q y-coordinate
   result := (Q y-coordinate) XOR (Q x-coordinate)
3. return result, go to step 1.
Recoomended to use with G, wich cofactor is 1.


User Account Creating Algoritm:

Input: login, password
Output: Account: {login, password (encrypted), EC public and private keys (encrypted)}

1. seed = login || separator || password;
2. AES_MasterKey = PRNGa(seed) (used 128bit elliptic curve);
2. EC_PrivateKey = PRNGb();
3. EC_PublicKey from EC_PrivateKey;
4. AES_EncryptedKey = EC_Encrypt(AES_MasterKey, EC_PublicKey);
5. EC_EncryptedKeys = AES_ECB_Encrypt(EC_PublicKey || EC_PrivateKey, AES_MasterKey);
6. result := AES_EncryptedKey || EC_EncryptedKeys.


Connection Establishment Algorithm:

Client is connection initializer.
Server is another one.
ECC is Elliptic Curve Cryptography.

1. Client sends 'admesconnectionrequest' - (step 0)
   Server receives 'admesconnectionrequest' - (step 100);
2. Server sends 'admesconnectionresponse' - (step 100)
   Client receives 'admesconnectionresponse' - (step 0);
3. Client sends EC_PublicKey(c) - (step 1)
   Server receives EC_PublicKey(c) - (step 101);
4. Server sends EC_PublicKey(s) - (step 101);
   Client receives EC_PublicKey(s) - (step 1);
5. Client sends his signed name with his encrypted name using ECC - (step 2)
   Server receives client's signed name with client's encrypted name using ECC - (step 102);
6. Server sends his signed name with his encrypted name using ECC - (step 102)
   Client receives server's signed name with server's encrypted name using ECC - (step 102);
7. Both client and server decide if they know each other and thust for each other
   (part of step 2/102);
8. Client sends encrypted and signed random number A, got from PRNGa, using ECC - (step 3)
   Server receives encrypted and signed random number A - (step 103);
9. Server sends encrypted and signed random number B, got from PRNGa, using ECC - (step 103)
    Client receives encrypted and signed random number B - (step 3);
10. Both clinet and server are authenticated and got SeesionKey is A XOR B;

Message Format:

Message: | ENCRYPTED_IV | SIGNATURE_LENGTH | SIGNATURE | ENCRYPTED_MESSAGE |

Sender get pseudo-random IV from EPNGa and encrypt message with AES-CBC using SessionKey;
Then, Sender perform XOR between IV and last 128bit-block of encrypted message
and use this value as integrity control. Integrity control is signed, using
EC_PrivateKey of sender.
Finally, Sender encrypt IV with AES-ECB using SessionKey.