> ## Documentation Index
> Fetch the complete documentation index at: https://docs.gethevn.com/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> HEVN accounts are non-custodial in both products. Self-serve (the General tab): the person who owns the email holds the only key and signs for themselves. Whitelabel (the Whitelabel and REST API tabs): the integrator's customer creates and owns their account through Sign in with HEVN, a HEVN-hosted popup on the integrator's site; the integrator's backend holds a developer key, operates linked accounts and books their payouts, and the account holder approves every payout in that popup. The developer key signs only for the integrator's own wallet; it never signs a client's money.
> Use HEVN's terms exactly. A rail is a bank route a client can request. A virtual account (bnk_) is an opened rail. Account details are what a payer needs in order to wire money, and arrive in a field named requisites. A client is a customer's own account linked to the integrator through Sign in with HEVN (POST /dapi/v1/connect/sessions, then POST /dapi/v1/clients/link); there is no API call that creates one. The business behind it is the integrator's customer. A contact is a saved destination; a beneficiary is the party at the far end of a fiat payout. Every departure of money is a payout, to a bank account or to a wallet alike.
> Never name a banking partner. Say 'a licensed banking partner'.
> There are no published fee rates, spreads or minimums. Prices come from a quote on a specific payment; direct pricing questions to HEVN rather than inventing numbers.
> The whitelabel API is at /dapi/v1 and takes a developer-key session plus an X-Hevn-Account header. Developer keys have an IP allowlist and no scopes. Remote transfers are at /api/v1/remote_spend_limit and take a remote transfer key (rsl_) in X-Api-Key, bounded by an onchain spend permission the account holder grants. They are different credentials and neither works on the other surface. The HEVN CLI is discontinued.

# Developer key

> Create a P-256 key in the app with its IP allowlist, load it on your server, and rotate it without downtime.

Your backend holds one credential: a P-256 private key. HEVN stores only the public half. That key
logs you in to `/dapi/v1` and signs the payments that leave your own integrator account. It never
signs for a client: a client's holder approves their own payouts in the
[sign-in window](https://docs.gethevn.com/whitelabel/sign-in-with-hevn.md#approve-a-payout).

## Create it in the app

Keys are created in the HEVN app — [`https://sandbox.gethevn.com`](https://sandbox.gethevn.com), or
[`https://app.gethevn.com`](https://app.gethevn.com) in production — under **Settings → Partner
program → Developer**. Nothing in this API creates one. The key opens a session that reaches every
client linked to you, and it authorizes money from your own wallet, so creating it takes a browser session of your own,
never a token this API minted.

Creation asks for one thing, the **IP allowlist**: the source addresses the key may be used from, 1
to 64 IPv4 addresses, IPv6 addresses or CIDR networks. It is frozen the moment the key exists. There
is no edit and no `PATCH`; a new egress range means a new key.

The browser generates the keypair and shows you the private half **once**. Save it then: HEVN never
holds it and cannot show it again. Write it to a file with mode `0600` on the machine that will use
it, out of images, repositories and logs.

The app adds the public half to your own account's signer in the same action, so there is nothing
else to wire up. One key covers every client linked to you, because what it does for a client is
authenticate your backend, not sign. An account can hold up to **five** keys at once, which is what
makes a rotation possible without downtime.

## What the key is

| Property | Value |
| - | - |
| Curve | **P-256**, also called `secp256r1` or `prime256v1` |
| Public key on the wire | **base64** (standard alphabet, padded) of the **DER SubjectPublicKeyInfo**, at most 4096 characters |
| Signature on the wire | **base64** of the **ASN.1 DER** ECDSA `(r, s)` over **SHA-256** of the message |
| Fingerprint | `sha256:<hex of sha256(DER)>` |
| Key id | a `dk_…` id, shown in the app |

> [!WARNING]
>
> PEM armor in a `publicKey` field is rejected, base64url is rejected, and a raw 64-byte `r‖s`
> signature — what WebCrypto and Java's P1363 mode produce — is rejected. Convert to DER before you
> base64-encode. The details are in [Signing](https://docs.gethevn.com/whitelabel/signing.md#signature-format).

## What a session from the key may do

Every `/dapi/v1` route is open to a session from any of your keys. What the key may **sign** is
narrower, and it is fixed by whose wallet it is:

| Operation | Who signs |
| - | - |
| A payout or swap from your integrator account | Your developer key, co-signed by HEVN — [Signing](https://docs.gethevn.com/whitelabel/signing.md) |
| An operator action on an escrow deal you run | Your developer key, co-signed by HEVN — [Escrow actions](https://docs.gethevn.com/whitelabel/escrow-actions.md) |
| A payout for a client | The client's holder, in the [sign-in window](https://docs.gethevn.com/whitelabel/sign-in-with-hevn.md#approve-a-payout). Nothing for your key to sign |

A confirm that would have your key sign for a client's wallet answers `403 account_not_controlled`.
Nothing is prepared and nothing is signed.

> [!WARNING]
>
> The key caps nothing by amount. Whatever reaches your server with the key can spend all of your own
> wallet, and read and configure every client linked to you. Approval controls on your side are
> yours to build — see
> [Accounts and control](https://docs.gethevn.com/whitelabel/accounts-and-control.md#what-this-means-for-your-product).

## The IP allowlist

The allowlist is the set of source addresses the key may be used from. HEVN canonicalises every entry
and drops duplicates, so `203.0.113.10` is stored as `203.0.113.10/32`.

Every request re-checks it. A call from an address outside the list is `403`, and so is a call whose
source address HEVN cannot determine — on a read as on a payment.

> [!WARNING]
>
> The allowlist cannot be edited. Enter the addresses your deployment will actually call from,
> including the ones an autoscaler adds. A perfectly good key and a perfectly good signature still
> answer `403` from an address you did not list, and a new NAT gateway is an expensive way to find
> that out.

Your edge must strip caller-supplied `X-Forwarded-For`, `X-Real-IP` and `CF-Connecting-IP` before
they reach HEVN, or the allowlist is checking a header the caller controls.

## Load it in your server

Every example on these pages reads the key from `HEVN_KEY_PEM` — the file you saved when the app
showed you the private half.

```python Python theme={null}
import base64, os
from cryptography.hazmat.primitives import serialization


def load_key():
    with open(os.environ["HEVN_KEY_PEM"], "rb") as handle:
        return serialization.load_pem_private_key(handle.read(), password=None)


def public_key_b64(key) -> str:
    spki = key.public_key().public_bytes(
        serialization.Encoding.DER,
        serialization.PublicFormat.SubjectPublicKeyInfo,
    )
    return base64.b64encode(spki).decode()
```

```javascript Node theme={null}
import { createPrivateKey, createPublicKey } from "node:crypto";
import { readFileSync } from "node:fs";

export function loadKey() {
  return createPrivateKey(readFileSync(process.env.HEVN_KEY_PEM));
}

export function publicKeyB64(key) {
  return createPublicKey(key).export({ type: "spki", format: "der" }).toString("base64");
}
```

```go Go theme={null}
func LoadKey() (*ecdsa.PrivateKey, error) {
	armored, err := os.ReadFile(os.Getenv("HEVN_KEY_PEM"))
	if err != nil {
		return nil, err
	}
	block, _ := pem.Decode(armored)
	parsed, err := x509.ParsePKCS8PrivateKey(block.Bytes)
	if err != nil {
		return nil, err
	}
	key, ok := parsed.(*ecdsa.PrivateKey)
	if !ok {
		return nil, errors.New("hevn: not a P-256 key")
	}
	return key, nil
}

func PublicKeyB64(key *ecdsa.PrivateKey) (string, error) {
	spki, err := x509.MarshalPKIXPublicKey(&key.PublicKey)
	if err != nil {
		return "", err
	}
	return base64.StdEncoding.EncodeToString(spki), nil
}
```

A successful `POST /dapi/v1/auth/challenge` is the proof the key is live and the allowlist covers this
host. See [Sessions](https://docs.gethevn.com/whitelabel/sessions.md).

## When a key is refused

Login answers the same refusal for every key problem — an unknown email, a key that no longer exists,
a call from an address outside the allowlist, a signer that is not attached, a bad signature — so an
attacker learns nothing from probing:

| Status | `code` | What to check |
| - | - | - |
| 401 | `invalid_credentials` | The email, that the key still exists on the account, that you are calling from an allowlisted address, and that you signed the proof string with that key |
| 400 | `request_expired` | `requestExpiry` must be in the future and at most 5 minutes ahead |

Once you are authenticated the refusals are specific, because by then HEVN knows who you are:

| Status | `code` | Cause |
| - | - | - |
| 403 | `forbidden` | The key behind this session was deleted, or the request came from an address outside its allowlist. Every `/dapi/v1` request re-checks both |
| 403 | `forbidden`, `details.reason = "developerSessionRequired"` | The bearer is not a platform access token — an ordinary API token, a refresh token, or a token with no key behind it |
| 403 | `key_not_registered` | The `publicKey` on a payment is not one of this account's keys |
| 403 | `account_not_controlled` | The operation would sign for a wallet your key does not control — a client's |
| 409 | `signer_not_attached` | The signer exists but is not attached to the wallet being spent from |
| 400 | `signature_invalid` | Wrong bytes or wrong encoding — see [Signing](https://docs.gethevn.com/whitelabel/signing.md#signature-format) |

The full list is in [Errors](https://docs.gethevn.com/whitelabel/reference/errors.md#developer-keys).

## Rotate a key

Keys are immutable and additive, so a rotation is a roll rather than an edit, and both keys work
while both are live.

**1. Create the second key**

In the app, with an allowlist covering the hosts that will use it. Save the private half. Nothing changes for running code.

**2. Switch your servers**

Deploy the new key file. Payments start carrying the new `publicKey`. An approval is bound to your
signer rather than to one key, so anything prepared just before the switch can still be confirmed
with either key while both are live.

**3. Delete the old key**

In the app. The old key stops logging in and stops authorizing money on the next request that
uses it.

> [!WARNING]
>
> Deleting a key **does** cut the sessions already minted from it. Every platform request re-reads the
> key, so the next call on an access token minted from a deleted key is a `403` — as is the
> `POST /dapi/v1/auth/refresh` that would have replaced it. That is the control to reach for when a
> *token* leaks, not only when a key does.

## Habits worth keeping

* Keep the private key in a secret manager and mount it at runtime; keep it out of images,
  repositories and logs.
* One key per environment, and one per deployment if you can — the `publicKey` on each payment tells
  you which one signed.
* Give each key the narrowest allowlist its job allows, and create the replacement before you move
  traffic to a new range.
* Never sign in a browser. The key can spend your own balance and act on every client linked to you;
  a browser is the wrong place for it. The browser's part is the
  [sign-in window](https://docs.gethevn.com/whitelabel/sign-in-with-hevn.md), which needs no key at all.
* Rehearse the roll before you need it. A rotation you have never run is not a control.

> [card] [Next: Sessions](https://docs.gethevn.com/whitelabel/sessions.md)
>
> Two calls to log in, and one header to act as any of your clients.


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