OP_2ROT - Rotating Top Three Pairs

11. OP_2ROT — Rotating Top Three Pairs

Overview

OP_2ROT is the pair-level version of OP_ROT. It operates on the top six items of the stack, treating them as three pairs. The bottom pair is moved to the top, while the upper two pairs shift down.

Opcode Reference

Opcode:     OP_2ROT
Hex:        0x71
Word:       2ROT
Input:      x1 x2 x3 x4 x5 x6
Output:     x3 x4 x5 x6 x1 x2
Stack Before: [ ..., x1, x2, x3, x4, x5, x6 ]
Stack After:  [ ..., x3, x4, x5, x6, x1, x2 ]

Execution Trace

After pushing 1–6: Stack: [ 1, 2, 3, 4, 5, 6 ]
After OP_2ROT:     Stack: [ 3, 4, 5, 6, 1, 2 ]

The bottom pair (1, 2) is moved to the top.

Use Case: Pair-Level Pipeline Processing

In scripts handling multiple (sig, pubkey) pairs:

<sig_A> <pub_A> <sig_B> <pub_B> <sig_C> <pub_C>
OP_2ROT
→ Stack: [ <sig_B>, <pub_B>, <sig_C>, <pub_C>, <sig_A>, <pub_A> ]

Now (sig_A, pub_A) — which was pushed first — is at the top for first processing.

Failure Conditions

• Requires at least 6 items on the stack.

Summary

OP_2ROT is the most stack-depth-intensive of the standard rotation opcodes, requiring six items. It is used for reordering three pairs of values, particularly in multisig pipeline scripts.