OP_RIPEMD160 - RIPEMD160 Hashing Directly

5. OP_RIPEMD160 — RIPEMD160 Hashing Directly

Overview

OP_RIPEMD160 applies the RIPEMD-160 hash function directly to the top stack element, producing a 20-byte output. Unlike OP_HASH160, no prior SHA-256 step is applied.

Opcode value: 0xa6 (decimal 166)
Output size: 20 bytes (160 bits)
Algorithm: RIPEMD-160 (RACE Integrity Primitives Evaluation Message Digest)

What is RIPEMD-160?

RIPEMD-160 was developed in the open academic community in Europe (Belgium) in 1996, partly as a response to concerns about SHA-1's origins within the NSA. It was designed to be a strengthened version of the original RIPEMD algorithm, itself derived from MD4.

Key design features:

• Two parallel lines of processing (unlike SHA-1's single pipeline)

• 5 rounds of 16 operations each (per pipeline = 80 operations total × 2 pipelines)

• Output: 160 bits (5 × 32-bit words)

• No known practical collision attacks as of 2024

RIPEMD160("hello") = 108f07b8382412612c048d07d13f814118445acd
RIPEMD160("") = 9c1185a5c5e9fc54612808977ee8f548b2258d31
RIPEMD160("The quick brown fox") = 37f332f68db77bd9d7edd4969571ad671cf9dd3b

RIPEMD-160 vs SHA Family

| Property | RIPEMD-160 | SHA-1 | SHA-256 | |