# `Cartouche.Solana.Signer.Ed25519`
[🔗](https://github.com/zenhive/cartouche/blob/main/lib/cartouche/solana/signer/ed25519.ex#L1)

Ed25519 signing backend using a local private key seed.

Uses OTP `:crypto` directly (available since OTP 24). This is the Solana
equivalent of `Cartouche.Signer.Curvy` for Ethereum.

## Examples

    iex> seed = Base.decode16!("9D61B19DEFFD5A60BA844AF492EC2CC44449C5697B326919703BAC031CAE7F60")
    iex> {:ok, sig} = Cartouche.Solana.Signer.Ed25519.sign("hello", seed)
    iex> byte_size(sig)
    64

# `get_address`

```elixir
@spec get_address(<<_::256>>) :: {:ok, <<_::256>>}
```

Get the 32-byte Ed25519 public key for the given seed.

## Examples

    iex> seed = Base.decode16!("9D61B19DEFFD5A60BA844AF492EC2CC44449C5697B326919703BAC031CAE7F60")
    iex> {:ok, pub} = Cartouche.Solana.Signer.Ed25519.get_address(seed)
    iex> Base.encode16(pub, case: :lower)
    "d75a980182b10ab7d54bfed3c964073a0ee172f3daa62325af021a68f707511a"

# `sign`

```elixir
@spec sign(binary(), <<_::256>>) :: {:ok, <<_::512>>}
```

Sign message bytes with the given 32-byte seed.

Ed25519 handles hashing internally (SHA-512), so the message is signed
as raw bytes with no external digest step.

Returns `{:ok, signature}` where signature is exactly 64 bytes.

## Examples

    iex> seed = Base.decode16!("9D61B19DEFFD5A60BA844AF492EC2CC44449C5697B326919703BAC031CAE7F60")
    iex> {:ok, sig} = Cartouche.Solana.Signer.Ed25519.sign(<<>>, seed)
    iex> Base.encode16(sig, case: :lower)
    "e5564300c360ac729086e2cc806e828a84877f1eb8e5d974d873e065224901555fb8821590a33bacc61e39701cf9b46bd25bf5f0595bbe24655141438e7a100b"

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*Consult [api-reference.md](api-reference.md) for complete listing*