Firo (FIRO): how it works, supply and reviews
In short
- Type
- Own blockchain; the Zcoin chain continued under the Firo name with no chain swap
- Issuance
- 6.25 FIRO per block until a cap of 21.4 million FIRO, then a tail emission of 1 FIRO per block
- Risks and caveats
- Binance halted FIRO trading in April 2025; Firo advised users to withdraw and self-custody.
- Checked
- 31 October 2026
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Key facts
- Ticker
- FIRO
- Official site
- firo.org
Key facts checked on 31 October 2026 against official sources.
What is Firo
Firo, called Zcoin until November 2020, is a proof-of-work cryptocurrency with its own blockchain, built for private payments. Its Lelantus Spark protocol hides balances, history and counterparties by default, and masternodes add ChainLocks and InstantSend.
Network and consensus
| Parameter | Details |
|---|---|
| Type | Own blockchain; the Zcoin chain continued under the Firo name with no chain swap |
| Launched | 2016, as Zcoin, using the Zerocoin privacy protocol |
| Consensus | Proof-of-work with FiroPoW, a GPU-oriented algorithm designed to resist ASICs and FPGAs |
| Block time | Target 2.5 minutes |
| Privacy protocol | Lelantus Spark, live on mainnet since January 2024 (earlier Zerocoin, Sigma and Lelantus) |
| Masternodes | Each masternode needs a refundable 1,000 FIRO collateral; quorums provide ChainLocks and InstantSend |
Supply and issuance
| Parameter | Details |
|---|---|
| Issuance | 6.25 FIRO per block until a cap of 21.4 million FIRO, then a tail emission of 1 FIRO per block |
| Block reward split | 70% masternodes, 5% miners, 15% development, 10% community (decided by community vote in 2024) |
| Development fund | 15% of the block reward funds development and adoption work |
What FIRO is used for
- FIRO is the native coin used to send and receive private payments on the Firo blockchain.
- Running a masternode requires a refundable collateral of 1,000 FIRO; masternodes earn part of the block reward.
- Part of each block reward goes to miners, a development fund and a community fund.
Who develops and governs Firo
- Founders
- Poramin Insom founded Zcoin (now Firo) in 2016
- Developer
- Core team; Reuben Yap has led strategy, development and research
- Governance
- Emission and block-reward changes are decided through community polls (ranked-choice voting in 2024)
- Funding
- Mainly a share of the block reward and donations; no institutional venture-capital funding
- Open source
- Source code on GitHub (firoorg/firo)
History
| Date | Event |
|---|---|
| 2016 | Launched as Zcoin, implementing the Zerocoin privacy protocol. |
| July 2019 | Deployed the Sigma privacy protocol, which removed Zerocoin's trusted setup. |
| 27 October 2020 | Zcoin announced its new name, Firo, with the ticker FIRO. |
| 30 November 2020 | The rebrand took effect; zcoin.io began redirecting to firo.org. |
| 28 January 2021 | ChainLocks activated at block 341100 to protect against 51% attacks. |
| 18 January 2024 | Lelantus Spark went live on mainnet. |
| 1 September 2024 | Community vote finalised a tail emission and a new block-reward split. |
| 16 April 2025 | Binance halted Firo trading, with a withdrawal grace period until 16 June 2025. |
Security and audits
- ChainLocks: masternode quorums sign blocks, so a block is final once signed and deep reorganisations are blocked.
- Lelantus Spark had two cryptography audits (HashCloak; Daniel (Linfeng) Zhao) and a code and implementation audit before launch.
- Firo runs a vulnerability bounty program for researchers.
- Past incidents: a Zerocoin flaw (2019), an inflation bug (2020), a 51% attack and a Lelantus attack (2021), and a Spark flaw found through responsible disclosure (2026).
Security incidents
| Date | What happened | Source |
|---|---|---|
| 9 April 2019 | Exploit: Zcoin's monitoring flagged irregular Zerocoin mints and spends of the 100 XZC denomination; a cryptographic flaw in the Zerocoin protocol let forged coins be created. Zerocoin spends were disabled. Funds returned: not stated | zcoin.io |
| 14 August 2020 | Exploit: A rogue miner exploited an inflation bug (CVE-2018-17144, merged from Bitcoin Core 0.14 code) at block 293526. A 2025 core-team note puts the inflation at 320,841.99803185 XZC. Funds returned: 168,101.68037465 XZC were recovered and burnt, leaving net inflation of 152,740.3176572 coins (core team note, 21 February 2025). | firo.org |
| 20 January 2021 | Exploit: Firo said its network was under a 51% attack and advised users not to transact until the network returned to normal; it said this was not a coding error. ChainLocks was activated on 28 January 2021. Funds returned: not stated | twitter.com |
| 26 February 2021 | Exploit: The team disabled Lelantus with its emergency switch after irregular behaviour and several suspicious transactions, which it called a sophisticated attack. Lelantus came back after the v0.14.6.0 hard fork in April 2021. Funds returned: not stated | forum.firo.org |
| 1 August 2026 | Exploit: A researcher disclosed a Spark flaw that allowed forging coins in multi-input transactions. Firo disabled multi-input spends; it found no evidence of inflation beyond about 200 FIRO minted by the researcher to validate the finding. Funds returned: not stated | firo.org |
Risks and caveats
- Binance halted FIRO trading in April 2025; Firo advised users to withdraw and self-custody.
- Some exchanges forfeit deposits sent directly from a Spark address (Firo names HTX); deposits should come from a transparent address.
- Pooling funds for a shared masternode means trusting the person who holds the 1,000 FIRO collateral.
- Firo is a proof-of-work chain and was hit by a 51% attack in January 2021, before ChainLocks.
Official links
- Website: firo.org
- Docs: firo.org/about/faq
- Source code: github.com/firoorg/firo
- Block explorer: explorer.firo.org
- Blog: firo.org/blog
- Governance forum: forum.firo.org
Questions and answers
What is Firo?
Firo is a proof-of-work privacy cryptocurrency with its own blockchain. Its Lelantus Spark protocol hides balances, history and who you pay by default.
Is Zcoin the same as Firo?
Yes. Zcoin announced the name Firo on 27 October 2020 and the rebrand took effect on 30 November 2020. Firo uses the same blockchain, with no chain swap; the ticker changed from XZC to FIRO.
What is the maximum supply of Firo?
Emission is 6.25 FIRO per block until a cap of 21.4 million FIRO, then a tail emission of 1 FIRO per block.
Who created Firo?
Poramin Insom founded Zcoin (now Firo) in 2016; Reuben Yap has led the project's strategy, development and research.
Has Firo been hacked?
Firo has disclosed several incidents: a Zerocoin flaw (2019), an inflation bug exploited by a miner (2020), a 51% attack and a Lelantus attack (2021), and a Spark flaw reported by a researcher (2026).
Sources
- Firo - Home
- Firo - FAQ
- Firo - Team
- Firo - Zcoin is becoming Firo (27 October 2020)
- Firo - We are now Firo! (30 November 2020)
- Firo - Finalized tokenomics (1 September 2024)
- Firo - ChainLocks activated (28 January 2021)
- Firo - Lelantus Spark is live (18 January 2024)
- Firo - Binance halts Firo trading (16 April 2025)
- Firo - Disclosure of bug in Zcoin (20 August 2020)
- Zcoin - Further disclosure on Zerocoin vulnerability (26 April 2019, Wayback)
- Firo on X - 51% attack notice (20 January 2021)
- Firo forum - Lelantus disabled temporarily (26 February 2021)
- Firo - New mandatory update v0.14.6.0 (15 April 2021)
- Firo - Lelantus reactivated (26 April 2021)
- Firo - Spark vulnerability mitigated (13 August 2026)
- Firo - 10 years in the making (20 September 2026)
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