type authKeyId struct {
	Id []byte `asn1:"optional,tag:0"`
}

type SignatureAlgorithm int

const (
	UnknownSignatureAlgorithm SignatureAlgorithm = iota

	MD2WithRSA  // Unsupported.
	MD5WithRSA  // Only supported for signing, not verification.
	SHA1WithRSA // Only supported for signing, and verification of CRLs, CSRs, and OCSP responses.
	SHA256WithRSA
	SHA384WithRSA
	SHA512WithRSA

	cert, err := ParseCertificate(pemBlock.Bytes)
	if err != nil {
		t.Fatalf("failed to parse certificate: %s", err)
	}
	if sa := cert.SignatureAlgorithm; sa != MD5WithRSA {
		t.Errorf("signature algorithm is %v, want %v", sa, MD5WithRSA)
	}
	if err = cert.CheckSignatureFrom(cert); err == nil {
		t.Fatalf("certificate verification succeeded incorrectly")
	}
	if _, ok := err.(InsecureAlgorithmError); !ok {

		{"KeyUsageDigitalSignature", Const, 0},
		{"KeyUsageEncipherOnly", Const, 0},
		{"KeyUsageKeyAgreement", Const, 0},
		{"KeyUsageKeyEncipherment", Const, 0},
		{"MD2WithRSA", Const, 0},
		{"MD5WithRSA", Const, 0},
		{"MarshalECPrivateKey", Func, 2},
		{"MarshalPKCS1PrivateKey", Func, 0},
		{"MarshalPKCS1PublicKey", Func, 10},
		{"MarshalPKCS8PrivateKey", Func, 10},
		{"MarshalPKIXPublicKey", Func, 0},

pkg crypto/x509, const KeyUsageKeyAgreement KeyUsage
pkg crypto/x509, const KeyUsageKeyEncipherment KeyUsage
pkg crypto/x509, const MD2WithRSA SignatureAlgorithm
pkg crypto/x509, const MD5WithRSA SignatureAlgorithm
pkg crypto/x509, const NotAuthorizedToSign InvalidReason
pkg crypto/x509, const RSA PublicKeyAlgorithm
pkg crypto/x509, const SHA1WithRSA SignatureAlgorithm

pkg crypto/x509, const KeyUsageEncipherOnly = 128
pkg crypto/x509, const KeyUsageKeyAgreement = 16
pkg crypto/x509, const KeyUsageKeyEncipherment = 4
pkg crypto/x509, const MD2WithRSA = 1
pkg crypto/x509, const MD5WithRSA = 2
pkg crypto/x509, const NotAuthorizedToSign = 0
pkg crypto/x509, const PEMCipher3DES = 2
pkg crypto/x509, const PEMCipher3DES PEMCipher
pkg crypto/x509, const PEMCipherAES128 = 3