# Introduction Welcome to the fhEVM Examples library. These examples span multiple categories and are designed to help you learn privacy-preserving smart contract patterns step by step. ## Start here * [**FHE 101 (Plain Language)**](https://sun-labs.gitbook.io/fhevm-hub/fhe-101) * [**Start Here**](https://sun-labs.gitbook.io/fhevm-hub/start-here) * [**Common Pitfalls**](https://sun-labs.gitbook.io/fhevm-hub/pitfalls) * [**Learning Paths**](https://sun-labs.gitbook.io/fhevm-hub/learning-paths) * Want to browse by topic? See [**Chapters**](https://sun-labs.gitbook.io/fhevm-hub/chapters). ## Example map ### Auctions | Example | Concept | Difficulty | | --------------------------------------------------------------------------- | --------------------------------------------------------- | ------------ | | [BlindAuction](https://sun-labs.gitbook.io/fhevm-hub/auctions/blindauction) | Sealed-bid auction with encrypted bids and public reveal | Advanced | | [DutchAuction](https://sun-labs.gitbook.io/fhevm-hub/auctions/dutchauction) | Dutch auction with descending price and encrypted reserve | Intermediate | ### Basic | Example | Concept | Difficulty | | ------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------- | ------------ | | [AntiPatternMissingAllowThis](https://sun-labs.gitbook.io/fhevm-hub/basic/antipatternmissingallowthis) | Missing FHE.allowThis breaks reuse of stored handles | Intermediate | | [AntiPatternMissingUserAllow](https://sun-labs.gitbook.io/fhevm-hub/basic/antipatternmissinguserallow) | Missing FHE.allow(user) blocks user decryption | Intermediate | | [AntiPatternViewOnEncrypted](https://sun-labs.gitbook.io/fhevm-hub/basic/antipatternviewonencrypted) | View functions return encrypted handles, not plaintext | Intermediate | | [EncryptMultipleValues](https://sun-labs.gitbook.io/fhevm-hub/basic/encryptmultiplevalues) | Store multiple encrypted values with a single proof | Beginner | | [EncryptSingleValue](https://sun-labs.gitbook.io/fhevm-hub/basic/encryptsinglevalue) | Store one encrypted value and grant permissions | Beginner | | [FHEAdd](https://sun-labs.gitbook.io/fhevm-hub/basic/fheadd) | Add two encrypted values with FHE.add | Beginner | | [FHECounter](https://sun-labs.gitbook.io/fhevm-hub/basic/fhecounter) | Encrypted counter using FHE.add and FHE.sub | Beginner | | [FHEEq](https://sun-labs.gitbook.io/fhevm-hub/basic/fheeq) | Compare two encrypted values using FHE.eq | Beginner | | [FHEIfThenElse](https://sun-labs.gitbook.io/fhevm-hub/basic/fheifthenelse) | Conditional selection on encrypted values using FHE.select | Beginner | | [FHESub](https://sun-labs.gitbook.io/fhevm-hub/basic/fhesub) | Subtract two encrypted values with FHE.sub | Beginner | | [HandleGeneration](https://sun-labs.gitbook.io/fhevm-hub/basic/handlegeneration) | Handles are opaque references; FHE ops create derived handles (symbolic execution) | Intermediate | | [HandleLifecycle](https://sun-labs.gitbook.io/fhevm-hub/basic/handlelifecycle) | Store encrypted handles and reuse them across calls | Intermediate | | [InputProofsExplained](https://sun-labs.gitbook.io/fhevm-hub/basic/inputproofsexplained) | Input proofs bind encrypted inputs to a contract and sender | Intermediate | | [PublicDecryptMultipleValues](https://sun-labs.gitbook.io/fhevm-hub/basic/publicdecryptmultiplevalues) | Public decryption flow for multiple encrypted values | Intermediate | | [PublicDecryptSingleValue](https://sun-labs.gitbook.io/fhevm-hub/basic/publicdecryptsinglevalue) | Public decryption flow for a single encrypted value | Intermediate | | [UserDecryptMultipleValues](https://sun-labs.gitbook.io/fhevm-hub/basic/userdecryptmultiplevalues) | User decryption flow for multiple encrypted results | Beginner | | [UserDecryptSingleValue](https://sun-labs.gitbook.io/fhevm-hub/basic/userdecryptsinglevalue) | User decryption flow for a single encrypted result | Beginner | ### Games | Example | Concept | Difficulty | | ------------------------------------------------------------------ | ----------------------------------------------------- | ------------ | | [FHEWordle](https://sun-labs.gitbook.io/fhevm-hub/games/fhewordle) | Encrypted letter comparison with branch-free feedback | Intermediate | ### Identity | Example | Concept | Difficulty | | ------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------- | ------------ | | [AccessControlGrants](https://sun-labs.gitbook.io/fhevm-hub/identity/accesscontrolgrants) | User-controlled FHE.allow() permissions | Intermediate | | [ComplianceRules](https://sun-labs.gitbook.io/fhevm-hub/identity/compliancerules) | Combining encrypted compliance checks with FHE.and() | Intermediate | | [CompliantERC20](https://sun-labs.gitbook.io/fhevm-hub/identity/complianterc20) | FHE.select() for branch-free compliant transfers | Advanced | | [EncryptedAgeVerification](https://sun-labs.gitbook.io/fhevm-hub/identity/encryptedageverification) | FHE comparison (le, ge) for threshold checks without revealing values | Beginner | | [ERC7984ERC20WrapperExample](https://sun-labs.gitbook.io/fhevm-hub/identity/erc7984erc20wrapperexample) | ERC7984ERC20Wrapper (ERC20 ↔ ERC7984) + KYC-gated wrap/unwrap | Advanced | | [ERC7984Example](https://sun-labs.gitbook.io/fhevm-hub/identity/erc7984example) | Minimal ERC7984 token with confidential mint + transfer | Beginner | | [ERC7984KycRestricted](https://sun-labs.gitbook.io/fhevm-hub/identity/erc7984kycrestricted) | OpenZeppelin ERC7984Restricted + public KYC allowlist (revert-based compliance) | Intermediate | | [ERC7984ObserverAccessExample](https://sun-labs.gitbook.io/fhevm-hub/identity/erc7984observeraccessexample) | ERC7984ObserverAccess for opt-in audit / compliance observers | Intermediate | | [IdentityRegistry](https://sun-labs.gitbook.io/fhevm-hub/identity/identityregistry) | Storing encrypted identity attributes (euint8, euint16, ebool) | Intermediate | | [SwapERC7984ToERC20](https://sun-labs.gitbook.io/fhevm-hub/identity/swaperc7984toerc20) | ERC7984 → ERC20 swap using public decryption + FHE.checkSignatures (KYC is public) | Advanced | | [SwapERC7984ToERC7984](https://sun-labs.gitbook.io/fhevm-hub/identity/swaperc7984toerc7984) | ERC7984 → ERC7984 swap using FHE.allowTransient across token contracts (KYC is public) | Intermediate | | [TransientAccessControl](https://sun-labs.gitbook.io/fhevm-hub/identity/transientaccesscontrol) | FHE.allowTransient() for one-transaction permissions between contracts | Intermediate | | [VestingWalletConfidentialExample](https://sun-labs.gitbook.io/fhevm-hub/identity/vestingwalletconfidentialexample) | Confidential vesting (ERC7984) + public KYC gating + factory/clones | Advanced |