With bitcoin's blockchain, each block's hash is computed with the previous block's hash. That makes all blocks an immutable chain.

This is not the first time people used a hash-chain. As far as I know, Git was already used it since 2005 for the commit-hash computing.

So, what is the earliest use of hash chains? Where did the idea of blockchain come from?


According to Bitcoin and Cryptocurrency Technologies (BaCT), the Princeton Bitcoin textbook, the block chain dates back to a "paper by Haber and Stornetta in 1991. Their proposal was a method for secure timestamping of digitaldocuments, rather than a digital money scheme." (BaCT p.15)

The chaining of Merkle trees instead of single documents was proposed in a later paper. (BaCT p.16)


Although the blockchain as it is used in Bitcoin is a new and novel concept, the idea of a chain of blocks in the field of cryptography goes back to symmetric block cipher modes of operation. Specifically, the common practice of cipher block chaining. This practice was first described in a standard from 1981, although it was almost certainly in use before then.

Although cipher block chaining is fundamentally different than the chain of blocks that Bitcoin uses, it is an example from cryptography where a change to an earlier block affects all subsequent blocks.

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