user80233: Are there any op codes or combination of opcodes that can be used instead of a digital signature when creating a transaction?

user208: Existing signature schemes in Bitcoin are already implemented as opcodes (OP_CHECKSIG and OP_CHECKMULTISIG in particular), so this question's formulation seems a bit off.
If you don't mind a transaction whose outputs can be taken by anyone, this is trivial - you can just create an output with a script that does not use any signature checking opcodes.
Perhaps what you want to ask is Is there a way to create secure transactions without using any of the explicit digital signature opcodes?.
The answer to that is almost certainly no. You would effectively need to implement a digital signature scheme by hand, rather than relying on the provided ones. Digital signature schemes are remarkably complicated, and likely far beyond what is possible inside Bitcoin's current scripting language.

80233: <p>Are there any op codes or combination of opcodes that can be used instead of a digital signature when creating a transaction?</p>
 208: <p>Existing signature schemes in Bitcoin <em>are</em> already implemented as opcodes (<code>OP_CHECKSIG</code> and <code>OP_CHECKMULTISIG</code> in particular), so this question's formulation seems a bit off.</p>

<p>If you don't mind a transaction whose outputs can be taken by anyone, this is trivial - you can just create an output with a script that does not use any signature checking opcodes.</p>

<p>Perhaps what you want to ask is <em>Is there a way to create secure transactions without using any of the explicit digital signature opcodes?</em>.</p>

<p>The answer to that is almost certainly <strong>no</strong>. You would effectively need to implement a digital signature scheme by hand, rather than relying on the provided ones. Digital signature schemes are remarkably complicated, and likely far beyond what is possible inside Bitcoin's current scripting language.</p>
