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Cryptography and PKI
Hashing
Hashing verifies integrity for data such as email downloaded files and files stored on a disk . A hash is a number created w/ a hashing algorithm, and is sometimes listed as a check sum
Two popular hashing algorithms used to verify integrity
Two popular hashing algorithms used to verify integrity are MD5 and SHA
HMAC ( Hash-based Message Authentication Code )
HMAC Verifies both integrity and authenticity of a message yes of shared secret
Remember this
Hashing is one way function that creates a string of characters. You cannot reverse the hash to re create the original file. Passwords are often stored as hashes instead of storing the actual password additionally applications often salt passwords with extra characters before hashing them
Remember this
Bcrypt & PBKDF2 stretching techniques that help prevent brute force and rainbow table attacks. Both salt the password with additional random bits
Do hashing algorithms encrypt
No hashing algorithms like MD5 SHA & HMAC dont encrypt
Remember this
Encryption provides confidentiality and helps ensure that data is viewable only by authorized users. This applies to any data at rest ( such as data stored in a database ) in transit being sent over a network
Steam vs block ciphers
Steam ciphers encrypt data a single bit or a single byte at a time in a stream. Block ciphers encrypt data in specific sizes blocks such as 64 bit or 128 bit blocks. Stream ciphers are more efficient than block ciphers when encrypting data in continuous stream
ECB
Weakest
CBC( Cipher Block Chaining )
Used by some symmetric block ciphers.
USES IV for randomization
Cipher Modes
ECB deprecated should not be used. CBC mode combines each block with the previous block when encrypting data and sometimes stuffers from pipeline delays. CTM mode com bbn ones IV with a counter to encrypt each block. GCM combines Counter mode with hashing techniques for integrity.
