eckey.h File Reference

P-256 private-key extraction from the two DER shapes tools emit: SEC1 ECPrivateKey (RFC 5915 3) and PKCS#8 PrivateKeyInfo (RFC 5958 2) wrapping a SEC1 key. More...

#include "common/bytes/span/span.h"
#include "common/platform/sys/syscall.h"

Go to the source code of this file.

Functions
int	wired_eckey_p256_priv (wired_span key_der, u8 out[32])
	Extract the 32-byte P-256 private scalar from key_der.
int	wired_eckey_ed25519_pkcs8_encode (const u8 seed[32], wired_obuf *out)
	Encode a 32-byte Ed25519 seed as an RFC 8410 7 OneAsymmetricKey DER SEQUENCE: version 0, privateKeyAlgorithm { id-Ed25519 }, privateKey OCTET STRING wrapping the CurvePrivateKey OCTET STRING(seed).
int	wired_eckey_curve25519_priv (wired_span key_der, u8 out[32])
	Extract the 32-byte Curve25519 private key from an RFC 8410 7 OneAsymmetricKey DER SEQUENCE (Ed25519 or X25519: the privateKeyAlgorithm OID is not inspected, matching wired_eckey_p256_priv's treatment of parameters).

Detailed Description

P-256 private-key extraction from the two DER shapes tools emit: SEC1 ECPrivateKey (RFC 5915 3) and PKCS#8 PrivateKeyInfo (RFC 5958 2) wrapping a SEC1 key.

Only the leading version INTEGER and the private key OCTET STRING are examined; parameters and the public key are ignored.

Also RFC 8410 7 OneAsymmetricKey encode/decode for Ed25519/X25519: the 32-byte key material is carried as-is (CurvePrivateKey), with no bit clamping applied at this layer – RFC 7748 5/RFC 8032 5.1.5 clamping is applied by the scalar-multiply and signing primitives themselves (src/tls/handshake/core/tls/x25519.c, src/crypto/asymmetric/ecc/ed25519/ ed25519_sign.c) on every use, so the imported bytes must stay unclamped to round-trip identically through re-export.

Function Documentation

wired_eckey_curve25519_priv()

int wired_eckey_curve25519_priv	(	wired_span	key_der,
		u8	out[32] )

Extract the 32-byte Curve25519 private key from an RFC 8410 7 OneAsymmetricKey DER SEQUENCE (Ed25519 or X25519: the privateKeyAlgorithm OID is not inspected, matching wired_eckey_p256_priv's treatment of parameters).

The returned bytes are exactly the imported CurvePrivateKey octets, unclamped: X25519 (RFC 7748 5) and Ed25519 (RFC 8032 5.1.5) both apply their clamping internally on every scalar use, not at import time.

Parameters

key_der	DER-encoded OneAsymmetricKey (unencrypted PKCS#8 shape).
out	receives the 32-byte private key.

Returns

1 on success; 0 on malformed DER or a key not exactly 32 bytes.

wired_eckey_ed25519_pkcs8_encode()

int wired_eckey_ed25519_pkcs8_encode	(	const u8	seed[32],
		wired_obuf *	out )

Encode a 32-byte Ed25519 seed as an RFC 8410 7 OneAsymmetricKey DER SEQUENCE: version 0, privateKeyAlgorithm { id-Ed25519 }, privateKey OCTET STRING wrapping the CurvePrivateKey OCTET STRING(seed).

No publicKey field or attributes are emitted.

Parameters

seed	the 32-byte Ed25519 private seed (unclamped, RFC 8032 5.1.5).
out	receives the encoded DER; out->len is set on success.

Returns

1 on success; 0 if out's capacity is too small.

wired_eckey_p256_priv()

int wired_eckey_p256_priv	(	wired_span	key_der,
		u8	out[32] )

Extract the 32-byte P-256 private scalar from key_der.

The outer SEQUENCE's version INTEGER selects the shape: 1 means SEC1 (RFC 5915 3), 0 means PKCS#8 (RFC 5958 2) whose privateKey OCTET STRING holds a SEC1 key.

Parameters

key_der	DER-encoded private key (SEC1 or unencrypted PKCS#8).
out	receives the 32-byte private scalar.

Returns

1 on success; 0 on malformed DER, a scalar not exactly 32 bytes, or an unsupported structure/version.