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Ethical hacking Chapter 12 - Encryption - Eric Vanderburg
The document discusses encryption and certificate management. It describes how certificates expire after a validity period, but can be renewed if the keys are still valid. Certificates can also be revoked for reasons like a user leaving a company or a private key being compromised. A Certificate Revocation List tracks revoked certificates. The document also outlines best practices for backing up keys and setting up a Microsoft Root Certificate Authority.
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Ethical hacking Chapter 12 - Encryption - Eric Vanderburg
- 1. Ethical Hacking CHAPTER12 – ENCRYPTION ERIC VANDERBURG
- 2. Expiration, Revocation, and Suspension of Certificates A period of validity is assigned to each certificate After that date, the certificate expires A certificate can be renewed with a new expiration date assigned If the keys are still valid and remain uncompromised Reasons to suspend or revoke a certificate A user leaves the company A hardware crash causes a key to be lost A private key is compromised
- 3. Expiration, Revocation, and Suspension of Certificates (continued) Certificate Revocation List (CRL) Contains all revoked and suspended certificates Issued by CAs Suspension of a certificate might be done when one or more parties fail to honor agreements Suspension makes it easier to restore if the parties come to an agreement at a later date
- 4. Backing Up Keys Backing up keys is critical If keys are destroyed and not backed up properly, encrypted business-critical information might be irretrievable The CA is usually responsible for backing up keys A key recovery policy is also part of the CA’s responsibility
- 5. Microsoft Root CA Available in Windows Server 2003 and Windows 2000 Server Steps for setting up a Microsoft Root CA Install the Certificate Services Note that after installing this service the name of the domain or computer cannot change Configuring a Windows server as a CA (four options) Enterprise root CA Enterprise subordinate CA Stand-alone root CA Stand-alone subordinate CA
- 6. Microsoft Root CA(continued) Steps for setting up a Microsoft Root CA (continued) Specify options to generate certificates, including Cryptographic Service Provider Hash algorithm Key length
- 7. Understanding Cryptographic Attacks Attacks studied so far are passive attacks Active attacks attempt to determine the secret key being used to encrypt plaintext Cryptographic algorithms are usually public Follows the open-source culture
- 8. Birthday Attack Old adage If 23 people are in a room, two will share the same birthday Birthday attacks are used to find the same hash value for two different inputs A birthday attack is used to reveal any mathematical weaknesses in hashing algorithms SHA-1 uses a 160-bit key Theoretically, it would require 280 computations to break SHA-1 has already been broken
- 9. Mathematical Attacks Properties of the algorithm are attacked by using mathematical computations Categories Ciphertext-only attack The attacker has the ciphertext of several messages but not the plaintext Attacker tries to find out the key used to encrypt the messages Attacker can capture ciphertext using a sniffer program such as Ethereal or Tcpdump
- 10. Mathematical Attacks (continued) Categories (continued) Known plaintext attack The attacker has messages in both encrypted form and decrypted forms This attack is easier to perform than the ciphertext-only attack Looks for patterns in both plaintext and ciphertext Chosen-plaintext attack The attacker has access to plaintext and ciphertext Attacker has the ability to choose which message to encrypt
- 11. Mathematical Attacks (continued) Categories (continued) Chosen-ciphertext attack The attacker has access to the ciphertext to be decrypted and to the resulting plaintext Attacker needs access to the cryptosystem to perform this type of attack
- 12. Brute Force Attack An attacker tries to guess passwords by attempting every possible combination of letters Requires lots of time and patience Password-cracking program John the Ripper
- 13. Man-in-the-Middle Attack Attackers place themselves between the victim computer and another host computer They then intercept messages sent from the victim to the host and pretend to be the host computer This type of attack follows this process Gloria sends her public key to Bruce, and you, the attacker, intercept the key and send Bruce your public key Bruce sends Gloria his public key. You intercept this key and send your public key to Gloria
- 14. Man-in-the-Middle Attack (continued) This type of attack follows this process (continued) Gloria sends an encrypted message to Bruce but uses your key You can decrypt the message with your private key You reencrypt the message using Bruce’s public key and send it to Bruce Bruce answers Gloria with another encrypted message with your public key You can decrypt the message with your private key You reencrypt the message using Gloria’s public key and send it to Gloria
- 15. Dictionary Attack Attacker uses a dictionary of known words to try to guess passwords There are programs that can help attackers run a dictionary attack
- 16. Replay Attack The attacker captures data and attempts to resubmit the captured data The device thinks a legitimate connection is in effect If the captured data was logon information, the attacker could gain access to a system and be authenticated
- 17. Understanding Password Cracking Password cracking is illegal in the United States It is legal to crack your own password if you forgot it You must first obtain the password file from the system that stores user names and passwords File is stored in the /Etc/Passwd or /Etc/Shadow directory for *NIX systems A dictionary attack can be performed on the file by using automated programs
- 18. Understanding Password Cracking (continued) Password cracking programs John the Ripper Hydra (THC) EXPECT L0phtcrack Pwdump3v2 Steps for cracking passwords Run the Pwdump2 program to get hash values of user accounts Perform a brute force attack using John the Ripper
- 19. Summary Cryptographyhas been in existence since the dawn of civilization Ciphertext: data that has been encrypted Cleartext or plaintext: data than can be intercepted and read by anyone Symmetric cryptography: uses one key to encrypt and decrypt data Examples: DES, DEA, 3DES, and AES Asymmetric cryptography: uses two keys, one key to encrypt and another to decrypt data Examples: RSA, Elgamal, Diffie-Hellman
- 20. Summary (continued) Digital Signature Standard (DSS): ensures that digital signatures can be verified PGP: free public key encryption program to encrypt e-mail messages Hashing algorithms are used to verify data integrity Public key infrastructure (PKI): structure made up of many different components used to encrypt data Digital certificate: binds a public key to information about its owner Issued by a Certificate Authority (CA)
- 21. Summary (continued) Active attacks Birthday attacks Brute force attacks Man-in-the-middle attacks Replay attacks Dictionary attacks