E-Commerce Security

Attacks on security:

Security attacks can be classified in the following two categories depending on the nature of the attacker.

• Passive attacks: The attacker can only eavesdrop or monitor the network.Typically, this is teh easiest form of attck and can be performed qithout difficulty. In many networking environam,ents, for eg, broadcast type networks sucha sEthernet and wireless networks
• Active Attacks: Thre attacker is not on.ly able to listen to the transmission but also able too actively alter or obstruct it. Furthermore,depoending on trhe attack's action, the following sub categories can be used to cover the majority of ATTacks

Other types of attacks on Security

• Eavesdropping: This attack is used to gain knowledge of the transmitted data. However, using an encryption scheme to protect the transmitted data can easily prevent this attack
• Traffic Analysis: The main goal of this attack is not to gain direct knowledge about the transmitted data but to extract information from the characteristics from the transmission, for e.g., amount of data transmitted, identity of the communicating nodes, etc. This information may allow the attacker to reduce sensitive information., for e.g., the rules of the communicating nodes, their position, etc. Unlike the previously described attack, this one is more difficult to prevent
• Impersonation:Here the attacker uses the identity of another node to gain unauthorized access to resource
• Replay: The attacker retransmits data previously transmitted by legitimate node
• Denial of service: This active attack aims at obstructing or limiting access to a certain resoource. This resource could be a specific node or service or the whole netwok

Digital Signatures

Digital signature is bascially a way to ensure that an e(lectronic document email,spreasheet,text file etc) is authentic.
Authentic means that you know who created the document and you know that it is not be altered in any way since that person created it.

Symmetric Key Systems

The process invovlved with symmetric key systems:

1. Create, distribute and store the symmetric private key securely
2. Sender creates a digital signature by hashing the plaintext and attcaching the resulting syring to the plaintext
3. Sender applies the fast symmetric encryption / decryption algorithm with the symmetric private key tpo the package (plaintext and attached digital signature) to produce the ciphertext. Authentication happens inherently because only the sender has the symmetric proivate key and can encrypt the package
4. Only the receiver holing the symmetric private key and can decrypt this package
5. Sender transfers the ciphertext. The private symmetric key is never transmitted over the unsecure communication lines
6. Receiver applies the same symmetric encryption / decryption algorithm with the same symmetric key(which the reciver already has) to the cophertext to produce the origibnal plaintext and digital signature. This authenticates whoever holds the ptovate key
7. Receiver detaches the digital signature form the plaintext
8. Recceiver creates a digital signature by hashing the plaintext
9. Receiver compares the two digitakl signatures to prove messaGE integrity (uhaltered data)

The process involved with asymmetric-key systems:

1. Create and distribute asymmetric public and private keys securely
2. The asymmetric private key is delivered to the owner
3. The asymmetric public key is strored in an X.500 database and managed by the Certification Authority(CA)
4. User must implicitly trust the secure creation, distribution and management of the keys
5. Further, if the creator and the person or system manging the keys is different than the end user must implicitly trust that the creator if the keys that he has actually deleted his copies
6. Create a digital signature by hashing the plaintext. Encrypt the resulting digital signature using the sender's asymmetric private key and attach the resulting string to the palintext(only the ssenvder has has creeated th edigital sidgnature)
7. Create a private symmetric key used only for this tranmsmission(the session key) and apply it and the symmetric encryption / decryption algorithm to the plaintext and attcahed encryptred digital signature to produce the ciphertext
8. The problem of sending the session key to the receiver must now be addressed
9. Make certain the sender has the CA's asymmetric public key
10. Interception of unencrypted request for the public key is a common form of attack
11. There may bve a whole hierarchy of certificates attesting to the validilty of the CA's public key
12. X.509 describes different methods for establishing user access to the CA public keys, all of which provide an entry point to spoofers and show that there is no system that guarantees the identity of the CA
13. Ask the CA for ther receivers asymmteric public key
14. The process is vulnerable to the main-in-the-middle attack
15. The receivers assymetric public key has been "digitally signed" by the CA
16. This means that tha CA has used the CA's assymetric private key to encrypt the receivers asymetric public key
17. Since only the CA holds the CA's Asymmetric private key, then the receiver asymmtric public key came from the CA
18. Once received, decrypt the receiver's asymmetric public key using the CA's asymmetric public key and an asymmetric encryption / decryption algorithm
19. Implicit trust in the CA and that the CA is not compromised are required
20. If the CA (When you requested the CA's public key did ypu actually receive the CA's public key or something else's compromised, the entire infrastructure is unusable
21. Those holding the public key can encrypt, but there is no way of knowing if the key has been compromised
22. Using the receiver asymmetric public key (now received from the CA) and decrypted and an asymmtric encrypion / decryption algorithm encrypt the session key
23. Only those holding the receiver public key can encrypt, but there is no way of knowing of the key has been compromised
24. Attach the encrypted sesion key to the ciphertext (which includes the previously encrypted digital signature)
25. The encrypted session key is transmitted acroess the unsecured network and is the target for various types of attacks
26. Receiver detaches the encryoted session key from the ciphertext
27. The ptroblem of decrpyting the session key by the receive must now be addressed
28. Make certain the receiver hast the CA's Asymmetric public key
29. The same coomments like above can be made here
30. Using the receivers asymmetric private key and the same asymmetric encryption / decryption algorithm, receiver decrypts the session key
31. Receiver applies the same symmetric encryption / decryption algorithm with the now unencrypted symmetric key (session key) to the ciphertext to produce the plaintext and attached hash of digital signature
32. Receiver detaches the hash from the plaintext
33. Receiver asks the CA for the sender's asymmetric public key
34. Once received, receiver decrypts the sender asymetric public key using the CA's public key and the correct asymnetric encryption / decryption algorithm
35. The same comments alike above can be made here
36. Using the sender's asymmetric public key and an asymmetric encrytion / decryption algorithm receiver decrypts the hash string
37. Create a digital signature by hashing the plaintext
38. Compare the two hashes to prove that the data has been altered
39. Transfer the package(ciphertext) that includes the digital signature and the attached encrypted session key