Secure Hashing Techniques - Introduction

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Secure hashing what is it ? why do we need it ?
where do we use it ? A set of secure hashing techniques there pros and cons and their comparisons.

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Secure Hashing Techniques - Introduction

  1. 1. SECURE HASHING TECHNIQUES By UdhayyaGethan.M 311511205309
  2. 2. SECURE HASHING • What ? • Why ? • How ?
  3. 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. 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. 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. 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. 7. Collision: Example • x = “Viva” • Y = “Vegas” • H(x) = H(y) = 2
  8. 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. 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. 10. Steps for hashing: • • • • • Padding Dividing Computing Initialize Looping
  11. 11. Example for Padding:
  12. 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. 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. 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. 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. 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. 17. Thank you

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