Symmetric Key Algorithms

You already learned about symmetric key ciphers and the major issue with symmetric keys. Read the section in this article on symmetric key encryptions to learn more about the advantages and disadvantages of symmetric keys. There is more information about symmetric key ciphers in this article that will be covered in more detail later in this unit, but this article will give you a preview of 3DES, IDEA, and AES ciphers. View the flashcard tool as well to better understand and to learn the terms used in cryptography such as plaintext, ciphertext, key, encryption, decryption, countermeasure, symmetric key encryption, and block cipher.

14. Digital Certificates

X.509 is a standard for PKI digital certificate formatting that includes specifics such as the public key certificates, certificate revocation list, and attribute certifications. There are four main types of digital certificates issued by a Certificate Authority, as shown in the chart.

Types of Digital Certificates

Digital Certificate Description
End-entity Certificates
  • Issued to specific entity
  • Bind a public key to entity listed on the certificate
  • Identity document provided by most PKI
  • Signed by CA
CA Certificates
  • Certificate for identifying public key for CA
  • Can be self-assigned or assigned by a superior CA
Cross-certification Certificates
  • Used by independent CA to establish peer-to-peer relationships
  • Tells user that connecting CA is okay to use
Policy Certificates
  • Traceable
  • Used in high security applications
  • Provide centrally controlled policy information