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)

• Start Here

• Common Pitfalls

• Learning Paths

• Want to browse by topic? See Chapters.

Example map

Auctions

Example	Concept	Difficulty
BlindAuction	Sealed-bid auction with encrypted bids and public reveal	Advanced
DutchAuction	Dutch auction with descending price and encrypted reserve	Intermediate

Basic

Example	Concept	Difficulty
AntiPatternMissingAllowThis	Missing FHE.allowThis breaks reuse of stored handles	Intermediate
AntiPatternMissingUserAllow	Missing FHE.allow(user) blocks user decryption	Intermediate
AntiPatternViewOnEncrypted	View functions return encrypted handles, not plaintext	Intermediate
EncryptMultipleValues	Store multiple encrypted values with a single proof	Beginner
EncryptSingleValue	Store one encrypted value and grant permissions	Beginner
FHEAdd	Add two encrypted values with FHE.add	Beginner
FHECounter	Encrypted counter using FHE.add and FHE.sub	Beginner
FHEEq	Compare two encrypted values using FHE.eq	Beginner
FHEIfThenElse	Conditional selection on encrypted values using FHE.select	Beginner
FHESub	Subtract two encrypted values with FHE.sub	Beginner
HandleGeneration	Handles are opaque references; FHE ops create derived handles (symbolic execution)	Intermediate
HandleLifecycle	Store encrypted handles and reuse them across calls	Intermediate
InputProofsExplained	Input proofs bind encrypted inputs to a contract and sender	Intermediate
PublicDecryptMultipleValues	Public decryption flow for multiple encrypted values	Intermediate
PublicDecryptSingleValue	Public decryption flow for a single encrypted value	Intermediate
UserDecryptMultipleValues	User decryption flow for multiple encrypted results	Beginner
UserDecryptSingleValue	User decryption flow for a single encrypted result	Beginner

Games

Example	Concept	Difficulty
FHEWordle	Encrypted letter comparison with branch-free feedback	Intermediate

Identity

Example	Concept	Difficulty
AccessControlGrants	User-controlled FHE.allow() permissions	Intermediate
ComplianceRules	Combining encrypted compliance checks with FHE.and()	Intermediate
CompliantERC20	FHE.select() for branch-free compliant transfers	Advanced
EncryptedAgeVerification	FHE comparison (le, ge) for threshold checks without revealing values	Beginner
ERC7984ERC20WrapperExample	ERC7984ERC20Wrapper (ERC20 ↔ ERC7984) + KYC-gated wrap/unwrap	Advanced
ERC7984Example	Minimal ERC7984 token with confidential mint + transfer	Beginner
ERC7984KycRestricted	OpenZeppelin ERC7984Restricted + public KYC allowlist (revert-based compliance)	Intermediate
ERC7984ObserverAccessExample	ERC7984ObserverAccess for opt-in audit / compliance observers	Intermediate
IdentityRegistry	Storing encrypted identity attributes (euint8, euint16, ebool)	Intermediate
SwapERC7984ToERC20	ERC7984 → ERC20 swap using public decryption + FHE.checkSignatures (KYC is public)	Advanced
SwapERC7984ToERC7984	ERC7984 → ERC7984 swap using FHE.allowTransient across token contracts (KYC is public)	Intermediate
TransientAccessControl	FHE.allowTransient() for one-transaction permissions between contracts	Intermediate
VestingWalletConfidentialExample	Confidential vesting (ERC7984) + public KYC gating + factory/clones	Advanced