SHA- Secure hashing algorithm
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This document outlines the Secure Hashing Algorithm (SHA), focusing on SHA-1, developed by NIST and NSA in 1993 as a federal information processing standard. It details the functioning of SHA-1, including its input requirements, operational steps, and the processing of 512-bit blocks through multiple rounds and iterations. The algorithm is used in various applications, such as secure password hashing and digital signatures.
![How SHA-1 works.?
Step 5.1 : Copy chaining variables A-E into variables
a-e.
Step 5.2 : Divide current 512-bit block into 16 sub-
blocks of 32-bits.
Step 5.3 : SHA has 4 rounds, each consisting of 20
steps. Each round takes 3 inputs-
512-bit block,
The register abcde
A constant K[t] (where t= 0 to 79)](https://image.slidesharecdn.com/sha-170910180513/85/SHA-Secure-hashing-algorithm-8-320.jpg)
![How SHA-1 works.?
Step 5.4 : SHA has a total of 80 iterations (4 rounds X 20 -
iterations). Each iteration consists of following operations:-
abcde = ( e +Process P + S5(a) + W[t] + K[t] ), a, S30(b) , c , d
Where,
abcde = The register made up of 5 variables a, b, c, d, e.
Process P = The logic operation.
St = Circular-left shift of 32-bit sub-block by t bits.
W[t[ = A 32-bit derived from the current 32-bit sub-block.
K[t] = One of the five additive constants.](https://image.slidesharecdn.com/sha-170910180513/85/SHA-Secure-hashing-algorithm-9-320.jpg)
![How SHA-1 works.?
The values of W[t] are calculated as follows :
For the first 16 words of W (i.e. t=0 to 15) , the
contents of the input message sub-block M[t] become
the contents of W[t].
For the remaining 64 values of W are derived using the
equation
W[t] = s1 ( W[t-16] XOR W[t-14] XOR W[t-8] XOR W[t-3])](https://image.slidesharecdn.com/sha-170910180513/85/SHA-Secure-hashing-algorithm-12-320.jpg)
SHA- Secure hashing algorithm
- 1. Internet Network Security Created by: Ruchi Maurya
- 4. Developed by NIST along with NSA In 1993, SHA was published as a Federal Information Processing Standard It has following versions- SHA-0 SHA-1 SHA-224 SHA-256 SHA-512 introduction
- 5. It works for any input message that is less than 264 bits. The output of SHA is a message digest of 160 bits in length. This is designed to be computationally infeasible to: Obtain the original message , given its message digest. Find two messages producing the same message digest SHA-1
- 6. How SHA-1 works.? Step 1: Padding of Bits Step 2: Append Length Step 3: Divide the input into 512-bit blocks
- 7. How SHA-1 works.? Step 4: Initialize chaining variables Step 5: Process Blocks- Now the actual algorithm begins…. Chaining Variables Hex values A 01 23 45 67 B 89 AB CD EF C FE DC BA 98 D 76 54 32 10 E C3 D2 E1 F0
- 8. How SHA-1 works.? Step 5.1 : Copy chaining variables A-E into variables a-e. Step 5.2 : Divide current 512-bit block into 16 sub- blocks of 32-bits. Step 5.3 : SHA has 4 rounds, each consisting of 20 steps. Each round takes 3 inputs- 512-bit block, The register abcde A constant K[t] (where t= 0 to 79)
- 9. How SHA-1 works.? Step 5.4 : SHA has a total of 80 iterations (4 rounds X 20 - iterations). Each iteration consists of following operations:- abcde = ( e +Process P + S5(a) + W[t] + K[t] ), a, S30(b) , c , d Where, abcde = The register made up of 5 variables a, b, c, d, e. Process P = The logic operation. St = Circular-left shift of 32-bit sub-block by t bits. W[t[ = A 32-bit derived from the current 32-bit sub-block. K[t] = One of the five additive constants.
- 10. How SHA-1 works.? Process P in each SHA round Round Process P 1 (b AND c) OR (( NOT b) AND (d)) 2 b XOR c XOR d 3 (b AND c ) OR (b AND d) OR (c AND d) 4 b XOR c XOR d
- 11. How SHA-1 works.? Single SHA-1 iteration
- 12. How SHA-1 works.? The values of W[t] are calculated as follows : For the first 16 words of W (i.e. t=0 to 15) , the contents of the input message sub-block M[t] become the contents of W[t]. For the remaining 64 values of W are derived using the equation W[t] = s1 ( W[t-16] XOR W[t-14] XOR W[t-8] XOR W[t-3])
- 13. Comparison
- 14. Application Secure password hashing Secure Socket Layer (SSL) security protocol Digital signature
- 15. https://brilliant.org/wiki/secure-hashing- algorithms/ https://www.tutorialspoint.com/cryptography/c ryptography_hash_functions.htm https://www.asd.gov.au/publications/protect/S HA-1_Deprecated.pdf References
- 16. Thank You !!