CertiGuide to Security+  9  Chapter 4:  Basics of Cryptography (Domain 4.0; 15%)

4.5.10.1  Multiple Key Pairs (Single, Dual) 1 2 3 4 5 6 4.7  Success Questions

Cryptographic Concepts

You learned about several concepts important to cryptography, including:

• Confidentiality, the ability to pass a message without unauthorized people who intercept it, understanding it, accomplished by encrypting with receiver’s private key; in symmetric crypto, confidentiality is limited because of the use of a shared key and the challenges of distributing it securely.
  
  
• Integrity, assurance that data has not been tampered with since it was encrypted, usually accomplished by encrypting with the sender’s private key; with symmetric crypto, anyone possessing the key can recreate and re-encrypt the message, destroying integrity.
  
  
• Authentication, verifying that a specific person sent a message).
  
  
• Non-Repudiation, a stronger variation on authentication, where the sender’s identity is verified by a third party, to prove that the message was not forged and make it impossible for the sender to deny sending it; you can prove message origin by encrypting the message or its hash value with the sender’s private key and decrypting with the sender’s public key.
  
  
• Digital Signature, an electronic signature of a document, created by calculating a document hash value with MD5 or SHA-1 that is encrypted with asymmetric crypto using the sender’s private key and an algorithm such as RSA; can be used to get data integrity and non-repudiation by having receiver decrypt signature using sender’s public key, compute the message hash value and verify that the has value and decrypted value are equal; you can digitally sign a message to get data integrity and non-repudiation WITHOUT encrypting the entire message to get confidentiality, or encrypt the message to get confidentiality as well.
  
  
• Access Control, for symmetric cryptography, all parties need to make sure the key is kept secure, which can be challenging; for asymmetric cryptography, the private key must be kept secure and if it is compromised, the key pair should be destroyed/revoked.

4.5.10.1  Multiple Key Pairs (Single, Dual) 1 2 3 4 5 6 4.7  Success Questions