> For the complete documentation index, see [llms.txt](https://docs.creditcoin.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.creditcoin.org/usc/creditcoin-oracle-subsystems.md).

# Creditcoin Oracle Subsystems

- [Readability](https://docs.creditcoin.org/usc/creditcoin-oracle-subsystems/readability.md)
- [Step 1: Attestation](https://docs.creditcoin.org/usc/creditcoin-oracle-subsystems/readability/step-1-attestation.md): USC Readability Step 1: The attestation subsystem of the Creditcoin Oracle achieves consensus about the confirmed state of a foreign chain and records that consensus on Creditcoin.
- [Continuity Proving for Attestation](https://docs.creditcoin.org/usc/creditcoin-oracle-subsystems/readability/step-1-attestation/continuity-proving-for-attestation.md): Continuity proofs make it possible to efficiently verify data from any block on a source chain. Without continuity proofs we would need to run 10-100x more consensus votes and store 100x more data.
- [Step 2: Transaction Proving](https://docs.creditcoin.org/usc/creditcoin-oracle-subsystems/readability/step-2-transaction-proving.md): USC Readability Step 2: The proving subsystem of the Creditcoin Oracle uses attestations and source chain blocks to prove that a particular transaction took place on a source chain.
- [Steps of Transaction Proving](https://docs.creditcoin.org/usc/creditcoin-oracle-subsystems/readability/step-2-transaction-proving/steps-of-transaction-proving.md)
- [Continuity Proving for Queries](https://docs.creditcoin.org/usc/creditcoin-oracle-subsystems/readability/step-2-transaction-proving/continuity-proving-for-queries.md): The Creditcoin Oracle uses Continuity proving to efficiently determine whether a given block is part of a source chain. It is the first of two key proofs that certify USC readability data.
- [Merkle Proving and Transaction Inclusion](https://docs.creditcoin.org/usc/creditcoin-oracle-subsystems/readability/step-2-transaction-proving/merkle-proving-and-transaction-inclusion.md): The Creditcoin Decentralized Oracle uses Merkle proving to determine whether a transaction is included in a given block. It is the second of two key proofs that certify oracle results.
- [Readability Gas Costs](https://docs.creditcoin.org/usc/creditcoin-oracle-subsystems/readability/readability-gas-costs.md): The on-chain verification of readability queries incurs normal gas costs for compute. We attempt to describe the scale and variance of those costs here.