# `./fio-stl/154 p256.h`

5 public symbols.

### Functions

#### `fio_ecdsa_p256_verify`

```c
int fio_ecdsa_p256_verify(const uint8_t *sig, size_t sig_len, const uint8_t *msg_hash, const uint8_t *pubkey, size_t pubkey_len)
```

Verifies an ECDSA P-256 signature.

**Parameters:**
- `sig` - DER-encoded signature (SEQUENCE { r INTEGER, s INTEGER })
- `sig_len` - Length of signature in bytes
- `msg_hash` - SHA-256 hash of the message (32 bytes)
- `pubkey` - Uncompressed public key (65 bytes: 0x04 || x || y)
- `pubkey_len` - Length of public key (must be 65)

**Returns:**
- 0 on success (valid signature), -1 on failure (invalid signature)

_Symbol type:_ `function`

#### `fio_ecdsa_p256_sign`

```c
int fio_ecdsa_p256_sign(uint8_t *sig, size_t *sig_len, size_t sig_capacity, const uint8_t msg_hash[32], const uint8_t secret_key[32])
```

Signs a message hash using ECDSA P-256.

**Parameters:**
- `sig` - Output: DER-encoded signature (max 72 bytes)
- `sig_len` - Output: actual signature length
- `sig_capacity` - Capacity of signature buffer (should be >= 72)
- `msg_hash` - SHA-256 hash of the message (32 bytes)
- `secret_key` - 32-byte secret key (scalar, big-endian)

**Returns:**
- 0 on success, -1 on failure

_Symbol type:_ `function`

#### `fio_ecdsa_p256_verify_raw`

```c
int fio_ecdsa_p256_verify_raw(const uint8_t r[32], const uint8_t s[32], const uint8_t msg_hash[32], const uint8_t pubkey_x[32], const uint8_t pubkey_y[32])
```

Verifies an ECDSA P-256 signature with raw r,s values.

**Parameters:**
- `r` - The r component of the signature (32 bytes, big-endian)
- `s` - The s component of the signature (32 bytes, big-endian)
- `msg_hash` - SHA-256 hash of the message (32 bytes)
- `pubkey_x` - X coordinate of public key (32 bytes, big-endian)
- `pubkey_y` - Y coordinate of public key (32 bytes, big-endian)

**Returns:**
- 0 on success (valid signature), -1 on failure (invalid signature)

_Symbol type:_ `function`

#### `fio_p256_keypair`

```c
int fio_p256_keypair(uint8_t secret_key[32], uint8_t public_key[65])
```

Generates a P-256 keypair for ECDHE key exchange.

**Parameters:**
- `secret_key` - Output: 32-byte secret key (scalar, big-endian)
- `public_key` - Output: 65-byte uncompressed public key (0x04 || x || y)

**Returns:**
- 0 on success, -1 on failure

_Symbol type:_ `function`

#### `fio_p256_shared_secret`

```c
int fio_p256_shared_secret(uint8_t shared_secret[32], const uint8_t secret_key[32], const uint8_t *their_public_key, size_t their_public_key_len)
```

Computes P-256 ECDH shared secret.

**Parameters:**
- `shared_secret` - Output: 32-byte shared secret (x-coordinate of result)
- `secret_key` - 32-byte secret key (scalar, big-endian)
- `their_public_key` - Their public key (uncompressed 65 bytes, or compressed 33 bytes)
- `their_public_key_len` - Length of their public key (33 or 65)

**Returns:**
- 0 on success, -1 on failure (invalid key, point at infinity, etc.)

_Symbol type:_ `function`

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