Cryptographic algorythms aka ciphers which comes fomr an arabic word sifr whcih means empty or zero.

**Certification Objective 2.8:**Summarize the basics of cryptographic concepts.

Use only proven cryptographic libraries. Homegrown methos generally don' t work.

Cutptographic operations include:

- Encryption for the protection of confidentiality
- Hashin foe the protection of integrity
- Digital signatures to mamage nonrepidiation
- Other specialy operations such as key exchanges

Deisigned to demostrate authenticity and identry associated with a mesage. Allow traceability to the person signing the message thorugh the use of their provate key.

Strength of cryptography typically depends on the strength of the key. A larger key with more entropy adds more strength to the encryption. Recommended minimum key lengths:

- Symmetric key lengths of at least 80 to 112 bits
- Eliptic curve key lengths of at least 160 to 224 bits
- RSA ley lengths of at least 2048 bits
- DSA key lengths of at least 2048 bits

Increases the computational complexity of a key by adding additional rounds of computation.

Concatenating additional pices of data to a key. Also known as initialization ventor (IV).

Mathematical function that perfoms one way encryption ie once the algorythmn is run there is no way to use the ciphertext to retrice the plantext. Also there is no way to generate the same ciphertext from two different plaintexts. Uses include: storing password and ensure message integrity. Popular has algorythmns include: Secure Hash Algorythomn (SHA) seeries, RIPEMD algorythmns, and the Message Digest (MD) hash of varing versions (MD2, MD4 & MD5).

Encryption and decryption is dependant on the exchnage of the key to decrypt the message. Symmetric encryption uses the same key to en/decrypt the message. Asymmetric en/decryption uses two separate keys. Diffie-Hellman method os one way to exchange keys in secure fashion. Depends on two random numbers each chosen by one of the parties.

An eliptic curve is defined by the funciton Y^2 = x^3 + ax^2 + b. Elliptic curves work because two points can be added to gether to get a third point on the curve. Works as a public key algorythmn. All public key systems rely on the difficulty of a certain math problem. ECC requires less computing power for a given bit strength, therefore good for low power mobile devices.

Property of a public key system in whcih a key derived from anouther key is not compromised even of the originating key is compromised in the future.

Use of quantum conputing hardware to perform en/decryption.

Keys that are used on once after generation.

Use some source o entrpy before encrypting sinsequeent blocks so that identical blcks of plaintext procude differing blocks of ciphertext. There are three groups:

**Authenticated:**designed to provide confidentiality and authenticity.**Counter:**function to generate a nonce that is used for each block encryption.**Unauthenticated:**Use a non-identoty based source for the entropy for subsquent blocks.

Distributed ledger that can record transactions and have bother verification of additions and protection of integrity.

Set of algorythomns used together in cryptography. Lists the key exchange mechanism, the authentication protocol, the block/stream cipher and message authentication.

Measure | Symmetric Encryption | Asymmetric Encryption |
---|---|---|

Primary Use | Bulk encryption of large quantities | Exchanging of symmetric keys |

Number of keys used | 1; the same key en/decrypts | 2; one key encrypts and a second key decrypts |

Common Algorythmns | AES, 3DES, RCA, IDEA | DSA, RSA, El Gamal, ECC, Diffie-Hellman |

Pros | Fast. Can be used for large quatities of data | Can be used without sharing a common secret. Used to exchange keys for summetric encryption. |

Cons | If the common key is lost then protection is lost | Slower. not good for large auantities of data. |

Specialized suite of algorithmns desinged to operate in the small device arana. ISO/IEC 29192 covers the methods of these.

Steganos is greek for "covered". Cooomn applicaiton is concealing text within a picture, audio or movie file.

Method of encoding information in an image while altering the actual visual image as little as possbile.

**Low Power Devices****Low Latency Devices****High Resiliency Devices****Support For Confidentiality****Suppoort for Integrity****Support for Obfuscation****Support for Authentication****Support for Nonrepudiation**

**Speed****Size****Weak Keys****Time****Lengevity****predictability****Reuse****Entropy****Computational Overhead****Resource vs Security Constraints****Weak/Deprecated Algorythomns**

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