Podcast
Questions and Answers
What is the range of indices for the first set of values in the SHA-1 message schedule?
What is the range of indices for the first set of values in the SHA-1 message schedule?
- 1 to 15
- 0 to 15 (correct)
- 0 to 20
- 1 to 16
How many rounds does the SHA-1 algorithm process each message block?
How many rounds does the SHA-1 algorithm process each message block?
- 40
- 10
- 20 (correct)
- 80
In the SHA-1 message schedule, what is computed for the indices greater than 15?
In the SHA-1 message schedule, what is computed for the indices greater than 15?
- A single value derived from $W_{j-16}$
- $W_{j-3}$ xor with the sum of the previous three values
- The direct copy of $W_{j-8}$
- A combination of four previous words using XOR operations (correct)
What is the size of the message block used in SHA-1?
What is the size of the message block used in SHA-1?
Which of the following correctly describes the output word $W_j$ when $j$ is less than or equal to 15?
Which of the following correctly describes the output word $W_j$ when $j$ is less than or equal to 15?
What is the main structure used by the SHA-1 algorithm to process message blocks?
What is the main structure used by the SHA-1 algorithm to process message blocks?
How does the SHA-1 algorithm use previous hash values in its process?
How does the SHA-1 algorithm use previous hash values in its process?
What is the role of the padding and length sequence in the SHA-1 algorithm?
What is the role of the padding and length sequence in the SHA-1 algorithm?
What is the final output of the SHA-1 algorithm referred to as?
What is the final output of the SHA-1 algorithm referred to as?
Which of the following statements about SHA-1's hash value is true?
Which of the following statements about SHA-1's hash value is true?
Flashcards
SHA-1 message schedule
SHA-1 message schedule
A process that generates 80 32-bit words (W0 to W79) from a 512-bit message block used in the SHA-1 algorithm.
Message Block
Message Block
A 512-bit chunk of input data processed during each stage of SHA-1.
W(j)
W(j)
A 32-bit word generated in the SHA-1 message schedule formula.
Round
Round
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SHA-1 Algorithm Stages
SHA-1 Algorithm Stages
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Message Schedule Formula
Message Schedule Formula
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Word Wj (j>15) calculation
Word Wj (j>15) calculation
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Hash Function
Hash Function
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SHA-1
SHA-1
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Message Digest
Message Digest
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Merkle-Damgård Scheme
Merkle-Damgård Scheme
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Compression Function (SHA-1)
Compression Function (SHA-1)
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Hash Value
Hash Value
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Message Block
Message Block
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Iterative Nature of SHA-1
Iterative Nature of SHA-1
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Padding and Length Sequence
Padding and Length Sequence
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Study Notes
SHA-1 Hash Function
- SHA-1 produces a 160-bit message digest.
- Preprocessing is needed before hash computation. The message is padded to fit a multiple of 512 bits. The initial value H₀ is set to a predefined constant.
- The compression function processes messages in 512-bit chunks. The function consists of 80 rounds, divided into four stages of 20 rounds each.
- Padding: The length of the message (l) is added to the padded message.
- A message schedule computes 80 32-bit words (W₀, W₁, ..., W₇₉) from the 512-bit message block.
- Wᵢ = { (Wᵢ₋₁₆ ⊕ Wᵢ₋₁₄ ⊕ Wᵢ₋₈ ⊕ Wᵢ₋₃) <<< 1 } for 16 ≤ j ≤ 79
- Five working registers (A, B, C, D, E) of size 32 bits.
- The hash value Hᵢ consists of five 32-bit words: H(0), H(1), H(2), H(3), H(4)
- The hash value initially holds the initial value H₀.
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