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![4. SHA Processing (contd.)
June 12, 2019 SHA-1 Algorithm 13
Source:
https://www.researchgate.net/publication/238180532_An_Architecture_for_a
_SHA1_Applied_for_DSA/figures?lo=1
Word assigning to other rounds:
For others (i.e round 16- 79)
W[t] = S1(w[t-16] XOR W[t-14] XOR W[t-8] XOR W[t-3])
For example: when round is 16,
• W[16] = S1(w[16-16] XOR W[16-14] XOR W[16-8] XOR W[16-3])
• Here W0, W2, W8 and W13 are XORed.
• The output is the new word for round 16.](https://image.slidesharecdn.com/sha-1algorithm-190612032648/85/SHA-1-Algorithm-13-320.jpg)
![4. SHA Processing (contd.)
June 12, 2019 SHA-1 Algorithm 13
Source:
https://www.researchgate.net/publication/238180532_An_Architecture_for_a
_SHA1_Applied_for_DSA/figures?lo=1
Word assigning to other rounds:
For others (i.e round 16- 79)
W[t] = S1(w[t-16] XOR W[t-14] XOR W[t-8] XOR W[t-3])
For example: when round is 16,
• W[16] = S1(w[16-16] XOR W[16-14] XOR W[16-8] XOR W[16-3])
• Here W0, W2, W8 and W13 are XORed.
• The output is the new word for round 16.](https://image.slidesharecdn.com/sha-1algorithm-190612032648/75/SHA-1-Algorithm-13-2048.jpg)
Uploaded byShiva RamDam
SHA 1 Algorithm
The document describes the SHA-1 hashing algorithm. SHA-1 produces a 160-bit hash value from an input of arbitrary length. It works by padding the input, appending the length, initializing hash buffers, processing the message through 80 rounds of compression, and outputting the final hash value. The compression function divides the padded message into 16-word blocks and schedules the words through the rounds using a message scheduling algorithm. It performs logical and bitwise operations on the words and chaining variables to generate a new hash.
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SHA 1 Algorithm
- 1. Message Digest Algorithm: SHA-1 Shiva Ram Dam MSc Information System Engineering June 12, 2019 Pokhara University Nepal
- 2. Introduction • SHA1: SecureHash Algorithm 1 • Designed by the United States National Security Agency • Produces hash value known as Message Digest 2June 12, 2019 SHA-1 Algorithm
- 3. Salient Features • Worksfor any input message that is less than 264 bits • produces160 bits length message digest • Infeasible to retain the original message from the message digest • Same message digest to be produced from both sender and receiver • Purpose: Authentication , not Encryption • widely used in security applications and protocols, including TLS, SSL, PGP, SSH, IPSec and S/MIME 3June 12, 2019 SHA-1 Algorithm
- 4. Message-Hashcode Example abc Abc 4June 12,2019 SHA-1 Algorithm a9993e36-4706816a-ba3e2571- 7850c26c-9cd0d89d 915858af-a2278f25-527f1920- 38108346-164b47f2 SHA
- 5. Abstract view ofSHA • Input to the SHA can be of arbitrary length. • Produces fixed length output (i.e. 160 bits length) June 12, 2019 SHA-1 Algorithm 5 SHA 1 Arbitrary Length H(X) 160 bits X
- 6. Steps: 1. Append paddingbits 2. Append Length 3. Initialize hash bufffer 4. SHA processing 5. Output June 12, 2019 SHA-1 Algorithm 6 Padding X (X1, X2, ….Xn) Compression Function 512 bits 160 bits H(X) 160 bits
- 7. 1. Padding Process ofadding extra bits (i.e. 0 followed after a 1) June 12, 2019 SHA-1 Algorithm 7 Padding X (X1, X2, ….Xn) Compression Function 512 bits 160 bits H(X) 160 bits Fig: Padding of string "abc" in bits
- 8. 2. Appending length •After padding, length of the message is represented in 24 bit • In total, the string is a multiple of 512 bits. June 12, 2019 SHA-1 Algorithm 8 Padding X (X1, X2, ….Xn) Compression Function 512 bits 160 bits H(X) 160 bits Fig: Padding of string "abc" in bits, finalized by the length of the string, which is 24 bits
- 9. • This 512bits input to the compression function • The message divided into 16 words. • Each word consists of 32 bits. • 512/32 =16 words June 12, 2019 SHA-1 Algorithm 9 Padding X (X1, X2, ….Xn) Compression Function 512 bits 160 bits H(X) 160 bits
- 10. 3. Initialize hashbuffer Initial values of Ho are predefined and stored in registers ABCDE These initial values are used in Round 0. June 12, 2019 SHA-1 Algorithm 10 H Hex values Ho(A) 01234567 Ho(B) 89ABCDEF Ho(C) FEDCBA98 Ho(D) 76543210 Ho(E) C3D2E1F0 Source: https://www.researchgate.net/publication/238180532_An_Architecture_for_a _SHA1_Applied_for_DSA/figures?lo=1 CF
- 11. 4. SHA Processing SHA1has 80 rounds defined. The Message Scheduler Algorithm schedules each word to rounds as: • W0 Round 0 • W1 Round 1 …… • W15 Round 15 • W16 Round 16 ….. • W79 Round 79 June 12, 2019 SHA-1 Algorithm 11 Wt is calculatedSource: https://www.researchgate.net/publication/238180532_An_Architecture_for_a _SHA1_Applied_for_DSA/figures?lo=1 Word assigning to rounds:
- 12. 4. SHA Processing(contd.) June 12, 2019 SHA-1 Algorithm 12 Source: https://www.researchgate.net/publication/238180532_An_Architecture_for_a _SHA1_Applied_for_DSA/figures?lo=1 Word assigning to round 0:
- 13. 4. SHA Processing(contd.) June 12, 2019 SHA-1 Algorithm 13 Source: https://www.researchgate.net/publication/238180532_An_Architecture_for_a _SHA1_Applied_for_DSA/figures?lo=1 Word assigning to other rounds: For others (i.e round 16- 79) W[t] = S1(w[t-16] XOR W[t-14] XOR W[t-8] XOR W[t-3]) For example: when round is 16, • W[16] = S1(w[16-16] XOR W[16-14] XOR W[16-8] XOR W[16-3]) • Here W0, W2, W8 and W13 are XORed. • The output is the new word for round 16.
- 14. 4. SHA Processing(contd.) Stages Round t=1 0 to 19 t=2 20 to 39 t=3 40 to 59 t=4 60 to 79 June 12, 2019 SHA-1 Algorithm 14 Each stage has 20 rounds. Source: https://www.researchgate.net/publication/238180532_An_Architecture_for_a _SHA1_Applied_for_DSA/figures?lo=1 Division of stages:
- 15. 4. SHA Processing(contd.) At each stage: June 12, 2019 SHA-1 Algorithm 15 Stage Predefined value of k t1 K1=0X5A827999 t2 K2= 0X6ED9EBA1 t3 K3=0X8F1BBCDC t4 K4=0XCA62C1D6 Source: https://www.researchgate.net/publication/238180532_An_Architecture_for_a _SHA1_Applied_for_DSA/figures?lo=1 Constant values:
- 16. 4. SHA Processing(contd.) Each round takes 3 inputs: • 32 bit word form 512 bit block (i.e.Wt) • The values from register ABCDE • Constant Kt June 12, 2019 SHA-1 Algorithm 16 Source: https://www.researchgate.net/publication/238180532_An_Architecture_for_a _SHA1_Applied_for_DSA/figures?lo=1 Process in each round:
- 17. 4. SHA Processing(contd.) Stage Ft t1 Ft(B.C,D) = (B AND C) OR ((NOT B) AND D) t2 Ft(B.C,D) = B XOR C XOR D t3 Ft(B.C,D) = (B AND C) OR (B AND D) OR (C AND D) t4 Ft(B.C,D) = B XOR C XOR D June 12, 2019 SHA-1 Algorithm 17 Source: https://en.wikipediaorg/wiki/SHA-1 Ft at different stages:
- 18. 4. SHA Processing(contd.) June 12, 2019 SHA-1 Algorithm 18 Source: https://en.wikipediaorg/wiki/SHA-1 • Output of Ft and E are added • Value in register A is 5 bit circular-left shifted. • This then added to previous sum. • Wt is added • Kt introduced • B is circular-left shifted by 30 bits. New values for next round At each Round: Denotes addition module 232
- 19. 5. The Output June12, 2019 SHA-1 Algorithm 19 • The 160 bit output from the final round is modulo added to the initial predefined values of Ho at registers ABCDE. • Output obtained thus is a 160 bit hash code. After Final Round: InitialvaluesofHo atABCDE 32 bits 32 bits 32 bits 32 bits 32 bits H(X) 160 bits
- 20. References • https://resources.saylor.org/wwwresources/archived/site/wp- content/uploads/2012/07/SHA-1-1.pdf • https://www.youtube.com/watch?v=YCf80-8xhGs •https://www.slideshare.net/karteek10/secure-hashing-algorithm • https://slideplayer.com/slide/8199025/ • https://www.slideshare.net/VishakhaAgarwal4/secure-hash-algorithm • https://brilliant.org/wiki/secure-hashing-algorithms/ • https://en.wikipedia.org/wiki/SHA-1 20June 12, 2019 SHA-1 Algorithm
- 21. QA session 21June 12,2019 SHA-1 Algorithm
- 22. Thank You 22June 12,2019 SHA-1 Algorithm