Deciphr Academy
Track 3 · Tokens · Module 15

Oracles

How blockchains learn prices and facts from outside, and how that gets attacked.

Lessons
6
Reading
39 min
Quiz
15 questions
Pass mark
80%
  1. 1The oracle problemWhat is a blockchain oracle, and what is the oracle problem?6 min
  2. 2How price feeds workHow does a crypto price feed get a price onto a blockchain?7 min
  3. 3Push and pull oraclesWhat is the difference between push and pull oracles?6 min
  4. 4Oracle networksWhat is an oracle network, and why use one instead of a single oracle?6 min
  5. 5Oracle manipulation: Mango MarketsHow was the Mango Markets oracle manipulated?7 min
  6. 6Choosing an oracleWhat should you check before relying on a price oracle?7 min

The case used in this module

Each module tells its own made-up Brindlecove story, so details can differ from one module to the next.

Key words

Oracle
A service that brings information from outside a blockchain, such as a price, to smart contracts.1
Oracle problem
The difficulty of making sure outside data is correct, available and honest, when a contract has to trust whoever supplies it.12
Price feed
An oracle that keeps a current price on-chain for contracts to read, such as ETH in US dollars.13
Aggregation
Combining many reports into one value, often by taking the median.45
Deviation threshold
How far, in percent, the outside price must move from the on-chain price before a feed updates.6
Heartbeat
The set time after which a feed starts an update even if the price has not moved.63
Push oracle
An oracle whose operator keeps sending price updates to the chain, at set times or after big moves.78
Pull oracle
An oracle whose signed prices wait off-chain until a user brings one on-chain in their own transaction.78
Decentralised oracle network
A group of independent oracle nodes that agree on a value before it goes on-chain.19
TWAP
Time-weighted average price: an average of a price over a period, so a short spike counts for little.102
Oracle manipulation
Pushing around the price an oracle reads, so a contract acts on a false value.112
Flash loan
A loan taken out and paid back within the same transaction.12
Sources
  1. Oracles. ethereum.org developer docs, page updated 26 June 2026.
  2. Smart contract security. ethereum.org developer docs, page updated 7 October 2026.
  3. What are Chainlink Data Feeds?. Chainlink documentation, page read 22 October 2026.
  4. Offchain Reporting. Chainlink documentation, page read 22 October 2026.
  5. How Pyth Pro Works. Pyth Network documentation, page read 22 October 2026.
  6. Decentralized Data Model. Chainlink documentation, page read 22 October 2026.
  7. Pull, Don't Push: A New Price Oracle Architecture. Pyth Network blog, 13 December 2022.
  8. What is Chainlink Data Streams?. Chainlink documentation, page read 22 October 2026.
  9. Chainlink 2.0: Next Steps in the Evolution of Decentralized Oracle Networks (whitepaper, v1.0). Chainlink Labs (Lorenz Breidenbach and others), 15 April 2021.
  10. Uniswap v2 Oracles. Uniswap developer docs, page read 22 October 2026.
  11. CFTC charges Avraham Eisenberg with manipulative and deceptive scheme to misappropriate over $110 million from Mango Markets. US Commodity Futures Trading Commission, press release 8647-23, 9 January 2023.
  12. What is DeFi?. ethereum.org, page updated 26 July 2026.