user88651: I am trying to unwrap bitcoin transaction generation process.
A bit confused about signing part.
My understanding is the transaction is sha256'd, then sha256'd one more time, then ECDSA'd. 
Based off https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm, ECDSA will first hash the message. Does that mean the transaction is sha256'd 3 times in total?
All the best!
Johnny

user52021: No, only two hashes. The hash itself isn't typically described as a part of ECDSA though the input must already be hashed (because e.g. a signature of 0 is trivially forged).

88651: <p>I am trying to unwrap bitcoin transaction generation process.</p>

<p>A bit confused about signing part.</p>

<p>My understanding is the transaction is sha256'd, then sha256'd one more time, then ECDSA'd. </p>

<p>Based off <a href="https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm</a>, ECDSA will first hash the message. Does that mean the transaction is sha256'd <strong>3</strong> times in total?</p>

<p>All the best!</p>

<p>Johnny</p>
 52021: <p>No, only two hashes. The hash itself isn't typically described as a part of ECDSA though the input must already be hashed (because e.g. a signature of 0 is trivially forged).</p>
