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73 Cards in this Set

  • Front
  • Back

Uses for Cryptography

Confidentiality, Data Integrity, Source Authentication, Non-repudiation
Non-repudiation
A sender cannot deny sending the message at a later date.
Cryptography
Science of hiding the meaning of communication
Cipher
Something that transforms characters into an unreadable format.
Work Factor
The time, effort, and resources needed to break a cryptosystem.
Properties of Symmetric Secret Key
All parties have the same shared secret key. Key distribution is difficult. Does NOT implement non-repudiation.
Scytale Cipher.
Coiled paper or parchment around a rod. Symmetric Cipher.
Properties of a Simple Substitution Cypher
Symmetric Cipher. Relies on simple substitution of characters or a transformation. Easier to crack based on pattern and frequency analysis. Can be Polyalphanumeric.
Vignerere Cipher
A polyalphanumeric symmetric cryptography based upon a grid and password or passphrase. If the password is shorter than the message was susceptible to frequency analysis.
Enigma Machine
A symmetric Cryptography used in WWII based on dials and rotors in a machine. Difficult to crack due to the complexity of the initial settings of the machine.
Vernam Cipher
One-Time Pads
Properties of One-Time Pads.
Symmetrical Cipher based upon a long string of characters on a page. If the message is shorter than the key and the pad is used only once, this method is theoretically impossible to decrypt.
Exclusive OR (XOR)
Logical "either/or," If both bits are the same, the result is 0, if both bits are different the result is 1.
Brute Force
Using every permutation.
A key of length n (bits) has how many combinations?
2n keys.
Breaking of DES
DES was broken by the Electronic Frontier Foundation in 3 days.
Confusion
When there is no simple correlation between the plaintext and the key.
Diffusion
When the same plaintext results in multiple changes spread throughout the ciphertext.
Kerckhoff's Principle
Cryptographic Algorithms should be public. Only Keys should be private,
Properties of Block Cipher
Message divided into blocks and each block encrypted separately. Can be symmetrical. Whole message is not encrypted as one entity. BEST FOR SOFTWARE
Some Properties of DES
Symmetric Block Cipher. 6x4 s-boxes.
Stream Cipher
Encrypts individual bits of the message, usually through XOR. Can be complex to implement. OFTEN USED IN HARDWARE ENCRYPTION.
Message Authentication Code (MAC)
authentication tag or CHECKSUM. Not the same as a digital signature.
Four types of Message Authentication Codes (MACS)
1. Unconditionally secure is similar to a one-time pad, 2. Hash-function HMAC - checksum appended to a message (e.g., MD-5), 3. Stream MAC, 4. Block-cipher MAC
Digital Signature
Message Digest (HASH) which is encrypted with the sender's PRIVATE key.
Digital Signature Standard (DSS)
Secure Hashing Algorithm developed by NIST. SHA is an example
SHA
Secure Hashing Algorithm. Used as a Digital Signature Standard (DSS).
Common Hashing or DSS standards
SHA, SHA-1, DSA, RSA, ECDSA
PKI
Public/private key pair cryptography. PUBLIC Key Cryptography.
Components of a PKI system
The CA, RA, Certificate Repository, and the Certificate Revocation System
X.509
Current standard for Digital Certificates
Steganography
The act of hiding information within other "normal" media such as photographs, documents, and music files.
Properties of Link Encryption
Full frames are encrypted. Often used for telecommunications. Not feasible over the internet since intermediate links are not secure.
Properties of End-to-End Encryption
Only the Payload of a frame is encrypted. Faster but more susceptible to sniffing.
Link versus End-to-End and the PSI model
Link usually happens at the lower levers (data/transport) while End-to-End usually happens at the higher levels (Presentation or Application).
How does PGP offer Confidentiality, Integrity, Authentication, and non-repudiation (offer actual methods)
C-IDEA, I-MD5, Auth-public ky certificates, Non-rep-cryptographically signed messages.
Major difference between S-HTTP and HTTPS
S-HTTP proects each message, not communication channel while HTTPS provides a secure channel.
SSL
Secure Sockets Layer. Encryption is SYMMETRICAL while peer's identity can vary on the protocol.
SSL occurs at which layer in the OSI model?
Transport
Steps for SSL connection
1-Server send client cert, 2-client checks if CA in cert is in table, 3-Client computes hash of cert with CA's public key, 4-Client check's cert's date, 5-Client confirms cert's URL, 6-Client extracts server's public key, 7-Client creates session key, 8-Client encrypts session key with server's public key, 9-Server decrypts session key with its private key.
S/MIME
Secure Multiple Internet Mail Extensions allows for encryption, hashing, and digital signatures in email
Properties of SSH
Secure Shell. A secure telnet often uses Diffie-Hellman as its key agreement protocol.
Secure Electronic Transaction
SET- Developed by Visa and Mastercard. Uses PKI.
IPSec
Sets up a secure channel between COMPUTERS instead of APPLICATIONS. Network Layer.
Avalanche Effect
Where a minor change in either the key or plaintext has a significant effect in the ciphertext.
Running Key Cipher
The key is repeated for the same length as the plaintext input.
Code versus Cipher
A code is a set meaning for the plaintext that might not be obvious (police 10 codes) where a cipher actually encrypts the plaintext.
Properties of DES
Data Encryption Standard. Symmetrical Key based on Harst Feistal. Became standard in 1977. Was replaced by AES. Key is 56 bits. Works on 64-bit input blocks.
Electronic Codebook Mode
Most basic form of DES. Normally only used for short messages. Each lock is encrypted independently.
Cipher Block Chaining Mode
CBC. Use of block encryption in DES where one block is used to encrypt the next block. Often used for Authentication.
CFB
Cipher Feedback Mode. A stream-based mode for DES. Often used for Authentication.
Disadvantage of DES
Susceptible to brute-force attacks. Was broken by the EFF in three days.
3DES
Triple DES. 2^112. Use two keys for encryption.
AES
Advanced Encryption Standard. Developed by NIST to replace DES and 3DES. Based on Rijndael.. Usually 128 bit.
IDEA
International Data Encryption Algorith. A replacement for DES.
Blowfish
Developed by Schneier. Symmetricl algorithm. Multiple-size keys.
RC5
Block cipher. Symmetrical.
RSA
Asymmetrical. Based on prime numbers.
Diffie-Hellmann Algorithm
Key exchange asymmetric algorithm. Based on logarithms.
El Gamal
Asymmetric Algorithm based onDiffie-Hellman. Often used for Digital Signatures.
ECC
Elliptical Curve Cryptography, Asymmetric. Often used in Smart Cards, wireless.
Checksum
Simple error detecting code
Hash Function
One-way cipher. Produces a message digest.
MD5
A hashing algorithm.
SHA, SHA-1
Secure Hash Algorithm. Developed by NIST for FIPS.
HAVAL
Australian Hashing Algorithm
RIPEMD-160
European Hashing Algorithm
Message Authentication Code
MAC. Checksum. Smaller than the overall message. Often generated (by DES) by the last block encrypted.
HMAC
Hashing Message Authentication Code.
Digital Signature
A message digest that is then encrypted using the sender's private key.
DSS
Digital Signature Standard. Developed by FIPS
ANSI X9.17
A standard Cryptographic Key Exchange methodology.
X.509
Standard PKI certificate