The ability to guarantey that a given message has not been modified from its original content.
Manual
Annotations:
Choose randomly pieces of message and compare. There is no 100% assurance and comparing all pieces would take too long.
CRC - Cyclic Redundancy Check
Annotations:
not suitable for security: they expect that unpredictable events damage single equioprobable bits randomly.
Digest
Annotations:
Computed summaries are compared
Cryptographic Hash
Annotations:
Uses Hash Functions to provide:
- performance
- one-way (not invertible)
- collision free -> impossible to achieve completely; alisiang probability is 1/(2^Nbit).
MD2
MD4
MD5
SHA-1
SHA-2
SHA-3
RIPEMD
Authentication
Protected Digest
MAC - Message Authentication Code
Annotations:
it can support also a MID (Message IDentifier) to avoid replay attacks. Must always be associated to a MAC to avoid changes to data.
Consider that this has not the purpose of guaranteing confidentiality!
The authentication is based on the use of a symmetric key. Only who knows the key can modify the MAC. Being based on a shared key it is not possible to provide non-repudiation.
Authentication by means of symmetric
encryption of the message
Authentication by means of symmetric
encryption of the message digest
Authentication by keyed-digest
based on Asymmetric Cryptography
Authentication by means of digital
signature
To provide both confidentiality and
authentication (+ integrity) combine
cryptography of data with symmetric alg and
use MAC
Different combinations of
authentication and encryption exists