---
title: "ECC Supported Curves"
source_url: https://dev.digicert.com/trustcore-sdk/crypto-interface/asymmetric-key-algorithms/ecc-supported-curves.html
---

With ECC, you must choose the domain parameters that define what curve you are going to work on when creating an empty key-shell. NanoCrypto supports the five curves defined by FIPS PUB 186-4 (P192, P224, P256, P384, P521) and the two Edward’s form curves defined in RFC 7748 (curve25519 and curve448).

To choose a curve, select the appropriate identifier from `${MSS_SRC_PKG}/src/crypto/ca_mgmt.h`:

- `cid_EC_P192`
- `cid_EC_P224`
- `cid_EC_P256`
- `cid_EC_P384`
- `cid_EC_P521`
- `cid_EC_X25519`
- `cid_EC_X448`
- `cid_EC_Ed25519`
- `cid_EC_Ed448`

Note that curve25519 and curve448 each have two identifiers, one for if the key will be used for signatures (edDSA, abbreviated in the identifier as `Ed`), and one for if the key will be used for key exchange (edDH, abbreviated in the identifier as `X`). For Edward’s curves, such keys are not interchangeable. Edward’s curves are not available for ElGamal.

For example, to create a key on curve P256, call the following:

```c
ubyte4 curveId = cid_EC_P256;
ECCKey *pKey = NULL;
CRYPTO_INTERFACE_EC_newKeyAux(curveId, &pKey);
```