Blockchain
Chaîne de blocs in French
Quick definition
A blockchain is a shared ledger of transactions, copied across many computers and secured by cryptography, so records can be trusted without a central bookkeeper. It is the technology underneath every cryptocurrency, and it says nothing about whether the assets riding on it have value.
A ledger kept by everyone
Strip away the jargon and a blockchain is a ledger: a running list of transactions, like the register of a chequing account. What makes it unusual is who keeps it. Instead of one bank holding the books, thousands of independent computers each hold a full copy, and they follow a shared set of rules, a consensus mechanism, to agree on which new transactions are valid before adding them.
New transactions are gathered into blocks, and each block is sealed with a cryptographic fingerprint that also includes the fingerprint of the block before it. That is the "chain": every block mathematically commits to the entire history behind it. Change one old entry and every fingerprint after it stops matching, which every computer on the network would notice immediately.
Hard to alter, and what that costs
This design makes the record genuinely hard to falsify: an attacker would need to overpower most of the network, not hack one server. That is a real achievement, and it is why the first working blockchain made cryptocurrency possible: bitcoin needed a ledger no single party controlled.
The honest trade-off is that all this duplication is expensive. Having thousands of computers store and verify every transaction is slower and costlier than a normal database run by one competent organization. A blockchain earns its keep only in one situation: when the participants cannot or will not trust a central party to keep the books. Where a trusted bookkeeper already exists, a regular database beats a blockchain on speed, cost and simplicity every time. Many disappointing corporate blockchain projects failed on exactly this point.
Public vs private chains
Public blockchains, like the ones behind the major cryptocurrencies, are open: anyone can read the ledger, submit transactions or help maintain it. Private (or permissioned) blockchains restrict participation to approved organizations, for example a group of banks sharing settlement records. Private chains are faster and more controllable, but critics note that once a small trusted group runs the ledger, the case for using a blockchain instead of a shared database becomes thin.
Beyond currency: experiments, with mixed results
Blockchains have been tried well beyond coins. Central banks and financial institutions, including in Canada, have run experiments settling payments and securities on distributed ledgers. Companies have piloted supply-chain tracking, recording a product's journey from origin to shelf. More recently, tokenized assets put traditional investments like fund units or bonds on a blockchain to speed up settlement. Some of this work continues seriously; it is also honest to say that many pilots from the enthusiasm years were quietly wound down after concluding that a conventional database served just as well. The technology has found real uses; it has not remade finance on the timeline once promised.
What a blockchain does not do
One distinction keeps investors out of trouble: the integrity of the ledger says nothing about the value of what is written on it. A blockchain can prove that you own a token and that the ownership record has not been tampered with. It cannot make that token worth anything. A worthless project's token sits on the same tamper-proof rails as a stablecoin backed by real reserves. "It's on the blockchain" is a statement about record-keeping, not about value, and marketing that blurs the two is a warning sign in itself.
In Canada
Canada has been an active experimenter: the Bank of Canada was among the first central banks to test settling interbank payments on distributed ledger technology, and Canadian securities regulators supervise the crypto trading platforms built on public blockchains. For most Canadians, though, blockchain matters indirectly: it is the plumbing beneath crypto assets and beneath a slice of financial-industry experimentation, not something a household interacts with on its own.
A plain-language illustration
Imagine a small town where, instead of one bank ledger, every resident keeps an identical copy of a shared notebook. When Ana pays Ben, she announces it to the whole town; everyone checks that Ana actually has the money, then writes the same line in their own copy. To cheat, Ana would have to convince most of the town to falsify their notebooks at once.
That is a blockchain: robust against tampering, but wildly inefficient compared with one trusted bookkeeper, since the whole town does the paperwork for every coffee purchased. The design is worth it only if the town has no bookkeeper everyone trusts. Note also what the notebook cannot do: it faithfully records that Ana gave Ben a "town point", but it has no opinion on whether a town point is worth anything.
Related terms
Reviewed by Alexandre Bernier, CFP®, CIM®, PFP®·Updated August 2026