Crypto SDK

The @smartholdem/crypto package handles everything cryptographic locally: key-pair derivation, transaction building & signing, hash-based message signing (ECDSA + Schnorr), and address / WIF utilities. No network calls.

Install

yarn add @smartholdem/crypto

Initialization

const { Identities } = require('@smartholdem/crypto')

// Throughout this document, the keys object used is:
const keys = Identities.Keys.fromPassphrase('this is a top-secret passphrase')

// The recipientId used in examples:
const recipientId = Identities.Address.fromPassphrase('this is a top-secret passphrase')

// The senderPublicKey used in examples:
const senderPublicKey = Identities.PublicKey.fromPassphrase('this is a top-secret passphrase')

Secrets never leave the device

Passphrases, private keys, and WIFs must never be transmitted over the network, logged, or committed to source control. Store them encrypted (AES-GCM or hardware-backed vault).

Transactions

A transaction is an object specifying the transfer of funds from the sender's wallet to the recipient's. Each transaction must be signed by the sender's private key to prove authenticity and origin. After broadcasting through the Client SDK, it is permanently incorporated into the blockchain by a Delegate Node.

Sign

The Crypto SDK signs a raw transaction object using your private key or passphrase. Familiarize yourself with digital signatures before you sign anything.

const { Transactions } = require('@smartholdem/crypto')

const transaction = {
  type: 0,
  amount: 200000000,
  fee: 100000000,
  recipientId,
  timestamp: 121212,
  asset: {},
  senderPublicKey
}

Transactions.Signer.sign(transaction, keys)
// >>> string (signature)

Serialize

Serialization produces the compact wire-format used inside blocks. If you combine the Crypto SDK with the Client SDK, you rarely need to serialize manually — .build().toJson() does it for you.

const { Transactions } = require('@smartholdem/crypto')

const transaction = Transactions.BuilderFactory
  .transfer()
  .amount(1000)
  .fee(100000000)
  .recipientId(recipientId)
  .senderPublicKey(senderPublicKey)
  .sign('sender')
  .build()

const serialized = Transactions.Serializer.serialize(transaction).toString('hex')
// >>> string

Deserialize

Deserialize only for inspection. The public API never returns serialized transactions.

const { Transactions } = require('@smartholdem/crypto')

const deserialized = Transactions.deserializer.deserialize(serialized)
// >>> ITransaction

Messages

The Crypto SDK can sign arbitrary strings — useful for off-chain proof-of-ownership, login challenges, and DeFi authorization flows.

Sign — ECDSA

const { Crypto } = require('@smartholdem/crypto')

const message = 'Arbitrary entry of data'
const hash = Crypto.HashAlgorithms.sha256(message)
const signature = Crypto.Hash.signECDSA(hash, keys)

const signed = { message, hash, signature }
// >>> IMessage

Sign — Schnorr

const { Crypto } = require('@smartholdem/crypto')

const message = 'Arbitrary entry of data'
const hash = Crypto.HashAlgorithms.sha256(message)
const signature = Crypto.Hash.signSchnorr(hash, keys)

const signed = { message, hash, signature }
// >>> IMessage

Verify — ECDSA

Crypto.Hash.verifyECDSA(
  signed.hash,
  signed.signature,
  '72b45a1978dd7669470ba67abbe5c220062924380c9c364b'
)
// >>> boolean

Verify — Schnorr

Crypto.Hash.verifySchnorr(
  signed.hash,
  signed.signature,
  '72b45a1978dd7669470ba67abbe5c220062924380c9c364b'
)
// >>> boolean

Identities

The Identities namespace derives and validates the four building blocks of a SmartHoldem wallet: Address, Public Key, Private Key, and WIF.

Address

const { Identities } = require('@smartholdem/crypto')

Identities.Address.fromPassphrase('this is a top secret passphrase')  // >>> string
Identities.Address.fromPublicKey('validPublicKey')                     // >>> string
Identities.Address.fromPrivateKey('validPrivateKey')                   // >>> string
Identities.Address.fromWIF('validWif')                                 // >>> string
Identities.Address.validate('validAddress')                            // >>> boolean

Private Key

Private keys and passphrases must remain private. Never store them unencrypted, minimize access, and consider hardware-signing for high-value wallets.

Identities.PrivateKey.fromPassphrase('this is a top secret passphrase')  // >>> string
Identities.PrivateKey.fromWIF('validWif')                                 // >>> string

Public Key

Public keys may be freely shared and are included in transaction objects for signature verification.

Identities.PublicKey.fromPassphrase('this is a top secret passphrase')  // >>> string
Identities.PublicKey.validate('validPublicKey')                          // >>> boolean

WIF (Wallet Import Format)

The WIF should remain secret — same threat model as passphrase and private key.

Identities.WIF.fromPassphrase('this is a top secret passphrase')  // >>> string

Cheat Sheet

From	Method	Returns
Passphrase	Identities.Keys.fromPassphrase(p)	Key-pair
Passphrase	Identities.Address.fromPassphrase(p)	Address
Passphrase	Identities.PublicKey.fromPassphrase(p)	Public key
Passphrase	Identities.PrivateKey.fromPassphrase(p)	Private key
Passphrase	Identities.WIF.fromPassphrase(p)	WIF
Public key	Identities.Address.fromPublicKey(pk)	Address
Private key	Identities.Address.fromPrivateKey(sk)	Address
WIF	Identities.Address.fromWIF(w)	Address
WIF	Identities.PrivateKey.fromWIF(w)	Private key

Next

• Client SDK — broadcast the transactions you just signed.
• Examples — end-to-end recipes combining Crypto + Client SDKs.