What does a TSA actually compute?
When a Time Stamping Authority processes a request, the computational work is minimal: receive a 32–64 byte hash, concatenate it with a UTC timestamp, sign with an RSA or ECDSA private key, and return the token. On modern hardware, this takes microseconds and a fraction of a milliwatt of electricity. A high-volume TSA handling 10 million timestamps per day consumes roughly the same power as a few desktop computers. The entire RFC 3161 transaction produces less than one millijoule of energy expenditure.
What a public blockchain actually computes
Bitcoin's Proof-of-Work consensus mechanism requires miners to repeatedly hash block headers until they find a value below a target threshold — a brute-force search with no shortcut. The Bitcoin network collectively performs approximately 500 exahashes per second (500 × 10¹⁸ SHA-256 operations per second) as of 2025. The Cambridge Centre for Alternative Finance estimates Bitcoin's annualised electricity consumption at 100–150 TWh per year — comparable to the electricity usage of a medium-sized country. Each Bitcoin transaction (which could embed a document hash in OP_RETURN) is responsible for roughly 700–1,000 kWh of energy, depending on mining mix.
Orders-of-magnitude difference
A single RFC 3161 timestamp consumes approximately 0.001 Wh (one milliwatt-hour). A Bitcoin OP_RETURN anchoring consumes approximately 700,000 Wh (700 kWh). That is a factor of 700 million between the two approaches for identical functional outcomes: proving a hash existed at a specific time. Even Ethereum's Proof-of-Stake (post-Merge 2022) consumes around 0.01–0.1 kWh per transaction — still 10 to 100 times more than a PKI timestamp. For organisations seeking green compliance credentials alongside document integrity, RFC 3161 is unambiguously the sustainable choice.
Legal equivalence with none of the footprint
An eIDAS-qualified timestamp from a QTSP carries full legal presumption across 27 EU member states under Article 41 of the eIDAS Regulation. A Bitcoin or Ethereum transaction has no equivalent legal status in the EU and requires expert evidence to be admitted in court. The qualified timestamp is both legally stronger and environmentally negligible. For compliance officers integrating ESG reporting with document management, this comparison is increasingly material in procurement decisions.