A user-chosen password that can be used with password-based encryption (PBE).
The password can be viewed as some kind of raw key material, from which the encryption mechanism that uses it derives a cryptographic key.
Different PBE mechanisms may consume different bits of each password character. For example, the PBE mechanism defined in PKCS #5 looks at only the low order 8 bits of each character, whereas PKCS #12 looks at all 16 bits of each character.
You convert the password characters to a PBE key by creating an instance of the appropriate secret-key factory. For example, a secret-key factory for PKCS #5 will construct a PBE key from only the low order 8 bits of each password character, whereas a secret-key factory for PKCS #12 will take all 16 bits of each character.
Also note that this class stores passwords as char arrays instead of
String objects (which would seem more logical), because the
String class is immutable and there is no way to overwrite its
internal value when the password stored in it is no longer needed. Hence,
this class requests the password as a char array, so it can be overwritten