# `CCXT.Signing.HmacSha256Iso`
[🔗](https://github.com/ZenHive/ccxt_client/blob/main/lib/ccxt/signing/hmac_sha256_iso.ex#L1)

HMAC-SHA256 with ISO timestamp and passphrase (OKX-style).

Used by: OKX, Coinbase, and ~10 other exchanges.

## How it works

1. Create ISO8601 timestamp
2. Build payload: `timestamp + METHOD + path + body`
3. Sign with HMAC-SHA256, encode as Base64
4. Send signature, API key, timestamp, and passphrase in headers

## Configuration

    signing: %{
      pattern: :hmac_sha256_iso_passphrase,
      api_key_header: "OK-ACCESS-KEY",
      timestamp_header: "OK-ACCESS-TIMESTAMP",
      signature_header: "OK-ACCESS-SIGN",
      passphrase_header: "OK-ACCESS-PASSPHRASE",
      signature_encoding: :base64
    }

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