Cryptography - Part 1 - Introduction and Hashing
About this episode
Information Security 1. Introduction ○ Security by obscurity § Steganography □ Hiding data inside another form of data, like using non-used bits in image to hide a message § Cool, but not practical. § Disadvantages ◊ Algorithm secrecy vs. key secrecy ○ Cryptography is everywhere and yet if done right, you can barely see it. ○ Goals: § Confidentiality □ Secrets stay secret. § Integrity □ Data is not tampered with. § Non-Repudiation □ No party can deny sending messages. § Authentication □ Each party can ensure that the sender is what they expect. ○ Cryptography § Hashing § Encryption § Signing § Protocols ○ Random Number Generators § Extremely important, almost all encryption/hashing strength is affected by how random the random number generator is. § Don't use simple random number, use a cryptographic random number generator with a sophisticated source of entropy. § Pseudorandom number generator § Dual_EC_DRBG random generator backdoor 2. Body ○ Hashing (one Way) § Properties □ Fixed length output no matter what size the input was □ Very easy to compute the hash of a given message, however very hard to compute from a hash the corresponding input. □ Mathematically infeasible to generate a message that has a given hash □ Any modification to a message produces a completely different hash that has no relationship to the original message's hash. □ It is mathematically infeasible to find two messages with the same hash. Hash Collision § Hashing Functions □ Provides data integrity, however lacks authentication □ Examples ® MD5 ◊ Considered Insecure ® Secure Hash Family SHA-X, Sha-1, Sha-2 [Sha256, Sha512], Sha-3 ◊ Sha-1 is considered insecure. ◊ Sha-1, Sha-2 designed by NSA ◊ Sha-3 is not designed by NSA, Competition winner. □ Attacks ® Brute force ◊ CPU's are getting faster and cheaper every day. ◊ GPU's are getting faster and cheaper every day. ◊ Special Hash calculating hardware is becoming more available especially with the BitCoin push. ® Rainbow table attacks ◊ Pre-Calculated tables where you can reverse lookup a hash to a value ◊ Try www.crackstation.net § Hash Message Authentication Codes (HMAC) □ Adds authentication to integrity □ Can be used with all previous algorithms, HMACMD5, HMACShA1, HMAC256 … etc. § Salted Hash □ Adds random salt to mitigate rainbow table □ Salts are unique per record, and not a secret. § Password Based Key Derivation Function (PBKDF2) □ RSA Public Key Cryptographic Standard PKCS #5 Version 2.0 □ Internet Engineering Task Force RFC 2898 Specification ® Adds a lot of iterations to slow it just enough to mitigate brute force (default 50,000 iterations) ® Adds random salt to mitigate rainbow table □ Disadvantage: It can be easily implemented with hardware which makes it vulnerable to bruteforce even with high number of iterations § Bcrypt □ Password Hashing function □ State of the art password hashing § Usages □ Integrity Check Password Storage Our facebook Page http://facebook.com/askdeveloper On Sound Cloud http://soundcloud.com/askdeveloper Please Like & Subscribe
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