Under the Hood: How Evolution-SDK Works

Fundamentals

Evolution-SDK library simplifies the process of building, signing and submitting Cardano transactions. This document explains the key components and processes that happen “under the hood”.

Every UTxO on Cardano must hold a minimum amount of ADA (lovelace), which increases with UTxO size (in bytes). This is particularly relevant for native tokens, as their data adds to the UTxO size.

const minLovelace = calculateMinLovelaceFromUTxO(
  coinsPerUtxoByte, // from protocol parameters
  utxo
);

Minimum ADA requirement acts as “rent” for blockchain storage, ensuring UTxOs cover their storage costs and preventing spam from tiny UTxOs (dust), which could bloat the blockchain state and degrade performance.

Transaction Building

Coin Selection Algorithm

When .complete() is called, Evolution-SDK internally queries available UTxOs in the connected wallet and selects “optimal” UTxOs to cover certain criteria for successful transaction building.

To be more specific, let’s take look at a basic case where the wallet has these UTxOs:

[
  { amount: 3_000_000n }, // 3 ADA
  { amount: 10_000_000n }, // 10 ADA
  { amount: 1_000_000n }, // 1 ADA
];

Fee Calculation

Fees are automatically calculated based on a few things. It can be about transaction size in bytes, number of inputs and outputs or execution units (if using smart contracts, more on that here).

• The base fee uses two protocol parameters, minFeeA (fee per byte of transaction size) and minFeeB (constant fee added to every transaction)
• Additional fees are added for reference scripts based on their size

// Draft the transaction to calculate the fee
const draftTx = await lucid
  .newTx()
  .pay.ToAddress("addr_test...", { lovelace: amount })
  .complete();
 
const fee = draftTx.toTransaction().body().fee();
 
// Build the final transaction using calculated fee
const finalTx = await lucid
  .newTx()
  .pay.ToAddress("addr_test...", { lovelace: amount - fee })
  .complete();

Integrations

CML

CML (Cardano Multiplatform Library) provides low-level primitives for Cardano blockchain interactions, and Evolution-SDK heavily leverages CML for various core functionality.

• Fee Estimation: Evolution-SDK uses CML for base fee calculation, while handling specific cases like script execution fees (via local UPLC or providers) and reference script fees internally.
• Key Management: For operations like deriving addresses from private keys, Evolution-SDK provides high-level APIs (like makeWalletFromPrivateKey), but you can also use CML directly for more granular control:

const pubKeyHash = CML.PrivateKey.from_bech32(privateKey)
  .to_public()
  .hash()
  .to_hex();

Noble Hashes

Evolution-SDK doesn’t expose hash functions directly. Instead, it recommends using the noble-hashes  library for cryptographic hashing needs, which is audited and secure.

• Compatible with both Node.js and browser environments
• Provides implementations of common hash functions including blake2b which is compatible with Aiken’s on-chain hash functions