Returns the name of the primary encoding format of this key,
or null if this key does not support encoding.
The primary encoding format is
named in terms of the appropriate ASN.1 data format, if an
ASN.1 specification for this key exists.
For example, the name of the ASN.1 data format for public
keys is <I>SubjectPublicKeyInfo</I>, as
defined by the X.509 standard; in this case, the returned format is
{@code "X.509"}. Similarly,
the name of the ASN.1 data format for private keys is
<I>PrivateKeyInfo</I>,
as defined by the PKCS #8 standard; in this case, the returned format is
{@code "PKCS#8"}.
Returns the name of the primary encoding format of this key, or null if this key does not support encoding. The primary encoding format is named in terms of the appropriate ASN.1 data format, if an ASN.1 specification for this key exists. For example, the name of the ASN.1 data format for public keys is <I>SubjectPublicKeyInfo</I>, as defined by the X.509 standard; in this case, the returned format is {@code "X.509"}. Similarly, the name of the ASN.1 data format for private keys is <I>PrivateKeyInfo</I>, as defined by the PKCS #8 standard; in this case, the returned format is {@code "PKCS#8"}.
@return the primary encoding format of the key.