[Crypto projects](https://revain.org/projects/) › Firo

# 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

## Key facts

- **Ticker**: FIRO
- **Official site**: [firo.org](https://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](https://web.archive.org/web/20190426184637/https://zcoin.io/further-disclosure-on-zerocoin-vulnerability/) |
| 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](https://firo.org/2020/08/20/disclosure-of-bug-in-zcoin.html) |
| 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](https://twitter.com/firoorg/status/1351703001849757697) |
| 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](https://forum.firo.org/t/lelantus-disabled-temporarily/1486) |
| 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](https://firo.org/2026/08/13/spark-vulnerability-mitigated.html) |

## 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](https://firo.org/)
- Docs: [firo.org/about/faq](https://firo.org/about/faq/)
- Source code: [github.com/firoorg/firo](https://github.com/firoorg/firo)
- Block explorer: [explorer.firo.org](https://explorer.firo.org/)
- Blog: [firo.org/blog](https://firo.org/blog/)
- Governance forum: [forum.firo.org](https://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](https://firo.org/)
- [Firo - FAQ](https://firo.org/about/faq/)
- [Firo - Team](https://firo.org/about/team/)
- [Firo - Zcoin is becoming Firo (27 October 2020)](https://firo.org/2020/10/27/zcoin-is-becoming-firo.html)
- [Firo - We are now Firo! (30 November 2020)](https://firo.org/2020/11/30/rebrand-is-live.html)
- [Firo - Finalized tokenomics (1 September 2024)](https://firo.org/2024/09/01/finalized-tokenomics-2024.html)
- [Firo - ChainLocks activated (28 January 2021)](https://firo.org/2021/01/28/chainlocks-activated-mainnet.html)
- [Firo - Lelantus Spark is live (18 January 2024)](https://firo.org/2024/01/18/spark-is-live.html)
- [Firo - Binance halts Firo trading (16 April 2025)](https://firo.org/2025/04/16/binance-delisting.html)
- [Firo - Disclosure of bug in Zcoin (20 August 2020)](https://firo.org/2020/08/20/disclosure-of-bug-in-zcoin.html)
- [Zcoin - Further disclosure on Zerocoin vulnerability (26 April 2019, Wayback)](https://web.archive.org/web/20190426184637/https://zcoin.io/further-disclosure-on-zerocoin-vulnerability/)
- [Firo on X - 51% attack notice (20 January 2021)](https://twitter.com/firoorg/status/1351703001849757697)
- [Firo forum - Lelantus disabled temporarily (26 February 2021)](https://forum.firo.org/t/lelantus-disabled-temporarily/1486)
- [Firo - New mandatory update v0.14.6.0 (15 April 2021)](https://firo.org/2021/04/15/software-update-014060.html)
- [Firo - Lelantus reactivated (26 April 2021)](https://firo.org/2021/04/26/lelantus-reactivated-on-firo.html)
- [Firo - Spark vulnerability mitigated (13 August 2026)](https://firo.org/2026/08/13/spark-vulnerability-mitigated.html)
- [Firo - 10 years in the making (20 September 2026)](https://firo.org/2026/09/20/firo-10-years-in-the-making.html)

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Page updated: 2026-10-31

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Source: https://revain.org/projects/firo/