user95279: Please explain why earlier the repeated values of "R" occurred in Bitcoin transactions.
For example, this transaction has a repetition of the value "R":
https://www.blockchain.com/btc/tx/19d66411a5aa716a04b37197c11c93c9446a54694a2d2302093d8b0a93ed5d83
If you look at RawTX:
https://btc.com/19d66411a5aa716a04b37197c11c93c9446a54694a2d2302093d8b0a93ed5d83.rawhex
repeat value "R":
R = cabc3692f1f7ba75a8572dc5d270b35bcc00650534f6e5ecd6338e55355454d5
What was the reason for this? Explain the reason for this error?

user48884: The R value is the result of EC point multiplication between the k value (known as the nonce) and the secp256k1 curve's generator point. It is effectively the public key for k. The only way that an R value can repeat is if k is also the same. Given that k is a 256 bit number and is supposed to be chosen completely randomly, k should not repeat unless the random number generator is broken.
Considering that k is generated at signing time and should be random, we can conclude that whoever chose k for those transactions has a faulty random number generator which is either outputting a fixed value or a small value which increases the probability of k being repeated. There is no good reason for this to happen, so this error comes from either a faulty RNG or a completely misunderstanding of how ECDSA works.

95279: <p>Please explain why earlier the repeated values of "R" occurred in Bitcoin transactions.</p>

<p>For example, this transaction has a repetition of the value "R":
<a href="https://www.blockchain.com/btc/tx/19d66411a5aa716a04b37197c11c93c9446a54694a2d2302093d8b0a93ed5d83" rel="nofollow noreferrer">https://www.blockchain.com/btc/tx/19d66411a5aa716a04b37197c11c93c9446a54694a2d2302093d8b0a93ed5d83</a></p>

<p>If you look at RawTX:
<a href="https://btc.com/19d66411a5aa716a04b37197c11c93c9446a54694a2d2302093d8b0a93ed5d83.rawhex" rel="nofollow noreferrer">https://btc.com/19d66411a5aa716a04b37197c11c93c9446a54694a2d2302093d8b0a93ed5d83.rawhex</a></p>

<p>repeat value "R":</p>

<p><strong>R = cabc3692f1f7ba75a8572dc5d270b35bcc00650534f6e5ecd6338e55355454d5</strong></p>

<p>What was the reason for this? Explain the reason for this error?</p>
 48884: <p>The <code>R</code> value is the result of EC point multiplication between the <code>k</code> value (known as the nonce) and the secp256k1 curve's generator point. It is effectively the public key for <code>k</code>. The only way that an <code>R</code> value can repeat is if <code>k</code> is also the same. Given that <code>k</code> is a 256 bit number and is supposed to be chosen completely randomly, <code>k</code> should not repeat unless the random number generator is broken.</p>

<p>Considering that <code>k</code> is generated at signing time and should be random, we can conclude that whoever chose <code>k</code> for those transactions has a faulty random number generator which is either outputting a fixed value or a small value which increases the probability of <code>k</code> being repeated. There is no good reason for this to happen, so this error comes from either a faulty RNG or a completely misunderstanding of how ECDSA works.</p>
