Information Systems Security Essentials (ISS611S) PDF

Information Systems Security Essentials (ISS611S) Chapter 2 - Cryptography  Contents Encryption Types of encryption algorithms Encryption Uses  Learning Outcomes Explain how encryption works Explain three ways used to obtain ciphe...

Information Systems Security Essentials (ISS611S) Chapter 2 - Cryptography  Contents Encryption Types of encryption algorithms Encryption Uses  Learning Outcomes Explain how encryption works Explain three ways used to obtain ciphertext Understand encryption uses in security Introduction What is encryption Introduction  Encryption Algorithm Y= F(x, k) Y = Ciphertext (scrambled information) X= Our original data known as plaintext K= Additional information used in the algorithm  Creating Ciphertext Ciphertext can be created using several methods: – Transposition - to change the relative position, order, or sequence of; cause to change places; interchange – Substitution - units of the plaintext (generally single letters or pairs of letters of ordinary text) are replaced with other symbols or groups of symbols – One-time pad - requires the use of a one-time pre-shared key the same size as, or longer than, the message being sent – The one-time pad be cannot be cracked? Transposition Ciphers  Substitution Ciphers xxxx  Plaintext - original message Ciphertext - coded message Cipher - algorithm for transforming Some Basic plaintext to ciphertext Terminology Key - info used in cipher known only to sender/receiver Encipher/encrypt - converting plaintext to ciphertext Decipher/Decrypt - recovering ciphertext from plaintext  Cryptography - study of encryption principles/methods Cryptanalysis (code breaking) - study of principles/methods of deciphering ciphertext without knowing key Some Basic Cryptology - field of both cryptography and Terminology cryptanalysis. Cryptosystem - involves a set of rules for how to encrypt the plaintext and decrypt the ciphertext. The encryption and decryption rules, called algorithms, often use a device called a key  Cryptography The The type type of of operations operations usedused for for transforming transforming plaintext plaintext to ciphertext to ciphertext Substitution Substitution Each Each element element in the in the plaintext plaintext is mapped is mapped intointo another another element element Transposition Transposition Elements Elements in the in the plaintext plaintext areare rearranged rearranged Cryptosystems Fundamental Fundamental requirement requirement is that is that no information no information be lost be lost are generically Product Product systems systems Involve Involve multiple multiple stages stages of substitutions of substitutions andand transpositions transpositions classified along The The number number of keys of keys usedused three Referred Referred to to encryption as as if symmetric, symmetric, both sender single-key, single-key, and receiver secret-key, secret-key, use the or conventional or conventional same key encryption if both sender and receiver use the same key independent Referred Referred to to as as asymmetric, asymmetric, two-key, two-key, or public-key or public-key encryption encryption if theifsender the sender andeach receiver use aeach use akey different key dimensions: and The The receiver wayway in which in which the the different plaintext plaintext is processed is processed Block Block cipher cipher processes processes thethe inputinputoneone block block of elements of elements at a at a time, time, producing producing an output block an output block for each input block for each input block Stream Stream cipher cipher processes processes thetheinputinput elements elements continuously, continuously, producing producing output output one element at a time, one element at a time, as it goes along as it goes along Types of Encryption Algorithms Hash Symmetric Asymmetric Symmetric Encryption Also referred to as conventional encryption or single-key encryption Was the only type of encryption in use prior to the development of public-key encryption in the 1970s Remains by far the most widely used of the two types of encryption Examples: Banking Applications, Data at rest (i.e., Disk encryption) Asymmetric Encryption Also referred to as public key encryption system Public-key cryptosystems uses two different keys. One for encryption and one for decryption. The keys are commonly known as a private key and a public key. The private key must remain confidential to its respective owner, while the public key is made available to everyone via a publicly accessible repository or directory. To decode an encrypted message, a computer must use the public key, provided by the originating computer, and its own private key. Used in Digital signatures and distribution of symmetric keys.  Symmetric Asymmetric DES RSA 3DES ElGamal AES elliptic Examples IDEA RC2/4/5/6 DH of Blowfish Encryption Each of these encryption algorithms algorithms have cryptographic keys that they use for encryption. The size/length of key influences it’s level of security.  Encryption Uses Confidentiality Authentication Digital Integrity signatures Public key certificate  Security Services Data Authentication Access Control Data integrity Nonrepudiation Confidentiality 13 Storch Street T: +264 61 207 2258 Private Bag 13388 F: +264 61 207 9258 Windhoek E: [email protected] NAMIBIA W: www.nust.na Summary  Homework Complete Chapter 1 Quiz Find online sources that discuss cryptography