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Evaluating the SHA-256 and Elliptic

Curve Digital Signature Algorithmsin Bitcoin Transactions

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Overview

What is a Bitcoin?

How do I get Bitcoins?

Bitcoin transactions SHA-256

ECDSA

Current price Q/A

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How do I get Bitcoins?

21-million Bitcoins

Designed to be an obtainable resource

Must be mined

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The Mint

Central authority that checksevery transaction

Contradictory?

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Secure Hash Algorithm

Designed by the U.S. National Security Agency

(NSA)

Transforms set of data elements into a fixed-

length value.

Verifies integrity of copies without needing to

derive original data

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SHA-256

Define

Preprocessing1. Append the bit 1 to the end of the message, followed by kzero bits, where kis the smallest non-negative solution to the

equation:

2. Parse the padded message intoN512-bit blocks:

3. The initial values of eight 32-bit words are initialized to the first 32 bits of the fractional parts of the square roots of the first

eight prime numbers:

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SHA-256 cont.

Steps:

1. The message schedule is prepared according to the equation:

2. Initialize the eight 32-bit working variables:

3. Perform the compression function for t = 0 to 63:

4. Compute the intermediate hash:

Final Hash:

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SHA Example

ASCII string: abc 448(24 + 1) =

Hex Representation:

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SHA Example Cont.

SHA-256 initial hash value:

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Elliptic Curve Digital Signature Algorithm

Public-key pairs

Key generation

Signature generation Signature verification

Weaknesses

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Signature Generation

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Signature Verification

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References

http://spectrum.ieee.org/computing/software

/bitcoin-the-cryptoanarchists-answer-to-cash

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