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where do we use it ? A set of secure hashing techniques there pros and cons and their comparisons.

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- 1. SECURE HASHING TECHNIQUES By UdhayyaGethan.M 311511205309
- 2. SECURE HASHING • What ? • Why ? • How ?
- 3. What is Hashing • A hash function is any algorithm that maps data of variable length of data to a fixed length. • The values returned by the hash functions are called as hash codes, hash sums, message digest or simply hashes. • Hashing mostly takes a string as an input and gives the output or the hashed values as a numerical value mostly as an hexadecimal number.
- 4. What is so special about Secure Hashing • Hash values produced by some hash techniques can be re hashed. • That means we can get the original data from the hash values. • But hash values of secure hash techniques cant be rehashed. • That’s why it is called as one way hashing.
- 5. Message Digest Functions: • Checksums fingerprint of a message • If message changes, checksum will not match • Most checksums are good in detecting accidental changes made to a message • They are not designed to prevent an adversary from intentionally changing a message resulting a message with the same checksum • Message digests are designed to protect against this possibility
- 6. One-Way Hash Functions: Example • M = “Elvis” • H(M) = (“E” + “L” + “V” + “I” + “S”) mod 26 • H(M) = (5 + 12 + 22 + 9 + 19) mod 26 • H(M) = 67 mod 26 • H(M) = 15
- 7. Collision: Example • x = “Viva” • Y = “Vegas” • H(x) = H(y) = 2
- 8. Criteria's for a hash function: • Given M, • it is easy to compute h • Given any h, • it is hard to find any M such that H(M) = h • Given M1, it is difficult to find M2 • such that H(M1) = H(M2) • Functions that satisfy these criteria are called message digest • They produce a fixed-length digest (fingerprint)
- 9. Secure Hashing Algorithm (SHA) : • SHA-0 • SHA-1 • SHA-2 1993 1995 2002 • SHA-224, SHA-256, SHA-384, SHA-512 SHA-1 A message composed of b bits 9 160-bit message digest
- 10. Steps for hashing: • • • • • Padding Dividing Computing Initialize Looping
- 11. Example for Padding:
- 12. Example : • M = 01100010 11001010 1001 (20 bits) • Padding is done by appending to the input – A single bit, 1 – 427 0s – A 64-bit integer representing 20 • Pad(M) = 01100010 11001010 10011000 … 00010100
- 13. Example : • Length of M = 500 bits • Padding is done by appending to the input: – A single bit, 1 – 459 0s – A 64-bit integer representing 500 • Length of Pad(M) = 1024 bits
- 14. Comparison: Output size (bits) Internal Block Max Word state size size message size Rounds Operations (bits) (bits) size (bits) (bits) Collisions found SHA-0 160 160 512 264 − 1 32 80 +, and, or, xor, rot Yes SHA-1 160 160 512 264 − 1 32 80 +, and, or, xor, rot None (252 attack) 256/224 256 512 264 − 1 32 64 +, and, or, xor, shr, rot None 512/384 512 1024 2128 − 1 64 80 +, and, or, xor, shr, rot None SHA-2
- 15. Some facts you must know: • Sha-512 is illegal to use in some countries. • Because it is tough even to the government to crack a 512 bit encryption. • Sha-0 and Sha-1 are very much prone to collision of data's. • Md5 hashing technique is no longer secure. • Md5 has been compromised. • It has a hash table about the size of 64Gb.
- 16. Applications of Secure Hashing: • • • • • Online Banking Online Shopping E-Learning Web servers ……… In short, wherever sensitive data's are handled and wherever you need to log yourself in to access data secure hashing is used there.
- 17. Thank you

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