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Basic Integrity and Authenticity - Coggle Diagram

- - - - The hash algorithm works as follows:
      - The sending device inputs the message into a hashing algorithm and computes its fixed-length hash of 4ehiDx67NMop9.
      - This hash is then attached to the message and sent to the receiver. Both the message and the hash are in plaintext.
      - The receiving device removes the hash from the message and inputs the message into the same hashing algorithm. If the computed hash is equal to the one that is attached to the message, the message has not been altered during transit. If the hashes are not equal, as shown in the figure, then the integrity of the message can no longer be trusted.
- - - - Two terms that are used to describe keys are:
      - Key length - Also called the key size, this is the measure in bits. In this course, we will use the term key length.
      - Keyspace - This is the number of possibilities that can be generated by a specific key length.
      - As key length increase, the keyspace increases exponentially:
      - A 2-bit (22) key length = a keyspace of 4 because there are four possible keys (00, 01, 10, and 11).
      - A 3-bit (23) key length = a keyspace of 8, because there are eight possible keys (000, 001, 010, 011, 100, 101, 110, 111).
      - A 4-bit (24) key length = a keyspace of 16 possible keys.
      - A 40-bit (240) key length = a keyspace of 1,099,511,627,776 possible keys.
- - - - The authentication objective of asymmetric algorithms is initiated when the encryption process is started with the private key.
      - The process can be summarized using the formula:
      - Private Key (Encrypt) + Public Key (Decrypt) = Authentication
      - When the private key is used to encrypt the data, the corresponding public key must be used to decrypt the data. Because only one host has the private key, only that host could have encrypted the message, providing authentication of the sender. Typically, no attempt is made to preserve the secrecy of the public key, so any number of hosts can decrypt the message. When a host successfully decrypts a message using a public key, it is trusted that the private key encrypted the message, which verifies who the sender is. This is a form of authentication.