Lecture CCNA Security - Chapter 7: Cryptographic systems

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After completing this chapter, students will be able to: Describe how the types of encryption, hashes, and digital signatures work together to provide confidentiality, integrity, and authentication; describe the mechanisms to ensure data integrity and authentication; describe the mechanisms used to ensure data confidentiality.

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Nội dung Text: Lecture CCNA Security - Chapter 7: Cryptographic systems

Chapter 7- Cryptographic Systems CCNA Security
Major Concepts • Describe how the types of encryption, hashes, and digital signatures work together to provide confidentiality, integrity, and authentication • Describe the mechanisms to ensure data integrity and authentication • Describe the mechanisms used to ensure data confidentiality • Describe the mechanisms used to ensure data confidentiality and authentication using a public key Học viện mạng Bach Khoa - Website: www.bkacad.com
Lesson Objectives Upon completion of this lesson, the successful participant will be able to: 1. Describe the requirements of secure communications including integrity, authentication, and confidentiality 2. Describe cryptography and provide an example 3. Describe cryptanalysis and provide an example 4. Describe the importance and functions of cryptographic hashes 5. Describe the features and functions of the MD5 algorithm and of the SHA-1 algorithm 6. Explain how we can ensure authenticity using HMAC 7. Describe the components of key management Học viện mạng Bach Khoa - Website: www.bkacad.com
Lesson Objectives 8. Describe how encryption algorithms provide confidentiality 9. Describe the function of the DES algorithms 10. Describe the function of the 3DES algorithm 11. Describe the function of the AES algorithm 12. Describe the function of the Software Encrypted Algorithm (SEAL) and the Rivest ciphers (RC) algorithm 13. Describe the function of the DH algorithm and its supporting role to DES, 3DES, and AES 14. Explain the differences and their intended applications 15. Explain the functionality of digital signatures 16. Describe the function of the RSA algorithm 17. Describe the principles behind a public key infrastructure (PKI) Học viện mạng Bach Khoa - Website: www.bkacad.com
Lesson Objectives 18. Describe the various PKI standards 19. Describe the role of CAs and the digital certificates that they issue in a PKI 20. Describe the characteristics of digital certificates and CAs Học viện mạng Bach Khoa - Website: www.bkacad.com
Secure Communications CSA Refer to 7.1.1.1 • The first goal for network administrators is to secure the network infrastructure, including routers, switches, servers, and hosts . • The next goal is to secure the data as it travels across various links Học viện mạng Bach Khoa - Website: www.bkacad.com
Secure Communications Secure communications involves a few primary tasks: 1. Authentication - Guarantees that the message is not a forgery and does actually come from who it states it comes from. 2. Integrity - Similar to a checksum function in a frame, guarantees that no one intercepted the message and altered it. 3. Confidentiality - Guarantees that if the message is captured, it cannot be deciphered. Học viện mạng Bach Khoa - Website: www.bkacad.com
Authentication • Authentication guarantees that a message comes from the source that it claims to come from. • Authentication can be accomplished with cryptographic methods. • Authentication is similar to entering a secure personal information number (PIN) for banking at an ATM • The PIN is a shared secret between a bank account holder and the financial institution. Refer to 7.1.1.2 Học viện mạng Bach Khoa - Website: www.bkacad.com
Authentication • What is the nonrepudiation ? Học viện mạng Bach Khoa - Website: www.bkacad.com
Non-repudiation • http://publib.boulder.ibm.com/infocenter/wmqv6/v6r0 /index.jsp?topic=/com.ibm.mq.csqzas.doc/sy10280_ .htm • If the sender of a message ever denies sending it, the non-repudiation service with proof of origin can provide the receiver with undeniable evidence that the message was sent by that particular individual. • If the receiver of a message ever denies receiving it, the non-repudiation service with proof of delivery can provide the sender with undeniable evidence that the message was received by that particular individual. Học viện mạng Bach Khoa - Website: www.bkacad.com
Authenticity versus nonrepudiation • Data nonrepudiation is a similar service that allows the sender of a message to be uniquely identified. • The most important part of nonrepudiation is that a device cannot repudiate, or refute, the validity of a message sent. • Nonrepudiation relies on the fact that only the sender has the unique characteristics or signature for how that message is treated. Học viện mạng Bach Khoa - Website: www.bkacad.com
Integrity • Data integrity ensures that messages are not altered in transit. • The receiver can verify that the received message is identical to the sent message and that no manipulation occurred. Học viện mạng Bach Khoa - Website: www.bkacad.com
Confidentiality Refer to 7.1.1.4 • Data confidentiality ensures privacy so that only the receiver can read the message. Encryption is the process of scrambling data so that it cannot be read by unauthorized parties. Học viện mạng Bach Khoa - Website: www.bkacad.com
Confidentiality • When enabling encryption, readable data is called plaintext, or cleartext, while the encrypted version is called ciphertext. • A key is required to encrypt and decrypt a message. The key is the link between the plaintext and ciphertext. • Using a hash function is another way to ensure data confidentiality. • What is the difference between hasing and encryption ? • The purpose of encryption and hashing is to guarantee confidentiality so that only authorized entities can read the message. Học viện mạng Bach Khoa - Website: www.bkacad.com
Cryptography • Cryptographic services are the foundation for many security implementations and are used to ensure the protection of data when that data might be exposed to untrusted parties. • Authentication, integrity, and confidentiality are components of cryptography. • The history of cryptography starts in diplomatic circles thousands of years ago. Học viện mạng Bach Khoa - Website: www.bkacad.com
Cipher • Each of these encryption methods use a specific algorithm, called a cipher, to encrypt and decrypt messages. • A cipher is a series of well-defined steps that can be followed as a procedure when encrypting and decrypting messages. • There are several methods of creating cipher text: 1. Transposition 2. Substitution 3. Vernam Học viện mạng Bach Khoa - Website: www.bkacad.com
Transposition Ciphers • In transposition ciphers, no letters are replaced; they are simply rearranged. • Modern encryption algorithms, such as the Data Encryption Standard (DES) and the Triple Data Encryption Standard (3DES), still use transposition as part of the algorithm. Học viện mạng Bach Khoa - Website: www.bkacad.com
Substitution Ciphers • Substitution ciphers substitute one letter for another. In their simplest form, substitution ciphers retain the letter frequency of the original message. Học viện mạng Bach Khoa - Website: www.bkacad.com
Substitution Ciphers: Caesar Cipher 1 FLANK EAST The clear text message would be ATTACK AT DAWN encoded using a key of 3. Clear text Shift the top scroll 2 over by three A B C D E F G H I J K L M N O P Q R S T U V W X Y Z characters (key of 3), an A becomes A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A B C D, B becomes E, and so on. 3 IODQN HDVW The clear text message would be DWWDFN DW GDZQ encrypted as follows using a key of 3. Cipherered text Học viện mạng Bach Khoa - Website: www.bkacad.com
Cipher Wheel 1 FLANK EAST The clear text message would be ATTACK AT DAWN encoded using a key of 3. Clear text 2 Shifting the inner wheel by 3, then the A becomes D, B becomes E, and so on. 3 IODQN HDVW The clear text message would appear DWWDFN DW GDZQ as follows using a key of 3. Cipherered text Học viện mạng Bach Khoa - Website: www.bkacad.com