Ed25519Derivation

public struct Ed25519Derivation : Sendable

Implements BIP-32 hierarchical deterministic key derivation for Ed25519 keys.

This struct provides Ed25519 key derivation following the BIP-32 standard, specifically for deriving Stellar keys using the path m/44’/148’/account’. The derivation uses HMAC-SHA512 to generate child keys from parent keys in a deterministic way.

The Stellar derivation path follows BIP-44:

  • Purpose: 44’ (hardened, meaning BIP-44)
  • Coin type: 148’ (hardened, Stellar’s registered coin type)
  • Account: n’ (hardened, user-defined account index)

All derivation levels use hardened keys (indicated by ‘), which means the parent private key is required to derive child keys, providing better security isolation.

See also:

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  • raw

    The derived private key material (32 bytes).

    Declaration

    Swift

    public let raw: Data
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  • The chain code used for deriving child keys (32 bytes).

    The chain code is additional entropy that ensures deterministic derivation while preventing knowledge of parent keys from child keys alone.

    Declaration

    Swift

    public let chainCode: Data
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  • Initializes the root derivation node from a BIP-39 seed.

    Creates the master key from a BIP-39 seed using HMAC-SHA512 with the key “ed25519 seed”. The first 32 bytes become the private key material, and the last 32 bytes become the chain code.

    Declaration

    Swift

    public init(seed: Data)

    Parameters

    seed

    A 512-bit (64-byte) seed generated from a BIP-39 mnemonic
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  • Derives a child key at the specified hardened index.

    Performs BIP-32 hardened derivation to generate a child key from the current key. Hardened derivation (index + 0x80000000) ensures that child keys cannot be derived from the parent public key, providing better security isolation between derivation levels.

    This method is used to traverse the BIP-44 derivation path:

    let masterKey = Ed25519Derivation(seed: bip39Seed)
let purpose = masterKey.derived(at: 44)      // m/44'
let coinType = purpose.derived(at: 148)      // m/44'/148'
let account = coinType.derived(at: 0)        // m/44'/148'/0'

    The derivation process:

    1. Prepends 0x00 to the parent private key
    2. Appends the hardened index (index + 0x80000000)
    3. Computes HMAC-SHA512 using the parent chain code as key
    4. First 32 bytes become the child private key
    5. Last 32 bytes become the child chain code

    Declaration

    Swift

    public func derived(at index: UInt32) -> Ed25519Derivation

    Parameters

    index

    The unhardened index (0-based). The method automatically applies hardening by adding 0x80000000 to the index.

    Return Value

    A new Ed25519Derivation representing the derived child key

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