I asked the same question in sCrypt slack. In the case of OP_PUSHTX, we can use any k number, so 1 is ok.
But we need to re-select the k value to ensure the r and s not equal to 0, according to <a href='https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm'>https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm</a> .
And the inversion of k can be computed off-chain, so there is no additional cost to use a random k.
I asked the same question in sCrypt slack. In the case of OP_PUSHTX, we can use any k number, so 1 is ok.
But we need to re-select the k value to ensure the r and s not equal to 0, according to <a href='https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm'>https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm</a> .
And the inversion of k can be computed off-chain, so there is no additional cost to use a random k.