Aiken Smart Contracts

aiken-smart-contracts

When to use

• Writing or auditing Aiken validators
• Building and testing smart contracts
• Generating .plutus artifacts for CLI/MeshJS

Operating rules (must follow)

• Confirm Aiken version before generating code
• Verify script hashes after every rebuild
• Test on preprod/preview before mainnet
• Treat datum/redeemer schemas as versioned APIs

Workflow

1. Initialize project

aiken new my-project
cd my-project

2. Project structure

my-project/
├── aiken.toml           # Project config
├── lib/                 # Reusable modules
├── validators/          # Validator entry points
│   └── my_validator.ak
└── plutus.json          # Generated blueprint

3. Write validator

// validators/my_validator.ak
use aiken/transaction.{ScriptContext}

validator {
  fn spend(datum: Data, redeemer: Data, ctx: ScriptContext) -> Bool {
    // Your validation logic
    True
  }
}

4. Build and test

# Build all validators
aiken build

# Run tests
aiken check

# Format code
aiken fmt

5. Generate artifacts

# Blueprint is auto-generated at plutus.json
# Extract .plutus for cardano-cli:
aiken blueprint convert > my_validator.plutus

# Get script hash
cardano-cli conway transaction policyid \
  --script-file my_validator.plutus

6. Derive script address

cardano-cli conway address build \
  --payment-script-file my_validator.plutus \
  --testnet-magic 1 \
  --out-file script.addr

Examples

Example: Simple spending validator

User request: "Create a validator that only allows spending by a specific pubkey"

Response:

// validators/pubkey_lock.ak
use aiken/hash.{Blake2b_224, Hash}
use aiken/transaction.{ScriptContext, Spend}
use aiken/transaction/credential.{VerificationKey}

type Datum {
  owner: Hash<Blake2b_224, VerificationKey>
}

type Redeemer {
  // Could be unit if no redeemer data needed
}

validator {
  fn spend(datum: Datum, _redeemer: Redeemer, ctx: ScriptContext) -> Bool {
    let ScriptContext { transaction, purpose } = ctx
    expect Spend(_) = purpose

    // Check if owner signed the transaction
    list.has(transaction.extra_signatories, datum.owner)
  }
}

# Build
aiken build

# Test
aiken check

# Generate .plutus
aiken blueprint convert > pubkey_lock.plutus

Example: Parameterized validator

User request: "Create a time-locked validator"

Response:

// validators/time_lock.ak
use aiken/interval.{Finite, Interval, IntervalBound}
use aiken/transaction.{ScriptContext, ValidityRange}

type Datum {
  lock_until: Int  // POSIX time in milliseconds
}

validator {
  fn spend(datum: Datum, _redeemer: Data, ctx: ScriptContext) -> Bool {
    let valid_range: ValidityRange = ctx.transaction.validity_range

    // Check if current time is past lock_until
    when valid_range.lower_bound.bound_type is {
      Finite(tx_earliest_time) -> tx_earliest_time > datum.lock_until
      _ -> False
    }
  }
}

V3 considerations (Conway)

• Single unified context argument
• Datum may be optional for some patterns
• Governance script purposes available
• Use aiken build --plutus-version v3 if targeting V3

Safety / key handling

• Datum/redeemer are on-chain visible—no secrets
• Version your datum schemas (breaking changes break funds)
• Verify script hash matches after any rebuild
• Always test with small amounts first

References

• shared/PRINCIPLES.md
• Aiken documentation
• cardano-cli-plutus-scripts (for deployment)