# C178 Cryptography 2a

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2018-01-14 17:04

## Section

Question | Answer |
---|---|

Modern cryptography is divided into three major areas: | symmetric cryptography, asymmetric cryptography, and hashing algorithms |

require both ends of an encrypted msg to have same key and processing algorithms | Symmetric algorithms |

generate a secret key that must be protected | Symmetric algorithms |

sometimes referred to as a secret key or private key | symmetric key |

a key that isn't disclosed to people who aren't authorized to use the encryption system | symmetric key |

what type of cryptographic algorithm is always faster than the other? | symmetric cryptographic algorithms |

can be just as secure with a smaller key size | symmetric cryptographic algorithms |

algorithm works on chunks of data, encrypts one and then moves to the next | block cipher |

data is encrypted one bit, or byte, at a time | stream cipher |

56-bit key, replaced by AES, considered insecure because of small key size | Data Encryption Standard (DES) |

more secure than DES, increases key length to 168 bits using 3 56-bit DES keys | Triple-DES (3DES) |

replaced DES as current standard, Rijndael algorithm, key sizes of 128, 192, 256 bits, with 128 bit default | Advanced Encryption Standard (AES) |

uses 256 bits instead of 128, qualifies for U.S. government as Top Secret | AES256 (AES-256) |

used by Microsoft and IBM, uses a 40-bit to 128-bit key, very fast and efficient | CAST (Carlisle Adams and Stafford Tavares) (128 and 256 also exist) |

uses a key size of up to 2048 bits, considered to be a strong system | RC5, also RC stands for Ron's Cipher, from RSA labs (RC4, RC5, and RC6) |

popular with wireless and WEP/WPA encryption, used in SSL and TLS, BitTorrent | RC4 |

symmetric block cipher that uses variable-length keys, performs a 64-bit block cipher very fast | Blowfish |

used in Pretty Good Privacy (PGP), public domain encryption system used for email | International Data Encryption Algorithm (IDEA) |

the only truly completely secure cryptographic implementation | One-time pad |

key exchanged within same communications channel that is going to be encrypted | In-band key exchange |

some other channel is used to exchange the key | Out-of-band key exchange |

ensures if one key is compromised subsequent keys will not be compromised | Forward secrecy |

uses two keys to encrypt and decrypt data | Asymmetric algorithms |

cannot be used to decrypt a message | public key |

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