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KDF

The KDF abstract class represent base class for all Key Derivation Functions. It is a parent of PBKDF2.

Instance Methods

KDF::__construct($length, $salt = NUL)

Description: Creates a new KDF class.

The KDF class is an abstract class which means that it can't be instantiated. This constructor defines just logic for its subclasses. It sets a supplied length and salt if supplied. It can throw KDFException if the salt size or length is over the max limits.

Parameters

length : int - the key length salt : string - the salt

Return value

KDF: New instances of the KDF subclass.

Throws

It can throw KDFException with code

  • KDFException::KEY_LENGTH_LOW - the supplied key length is too low
  • KDFException::KEY_LENGTH_HIGH - the supplied key length is too high
  • KDFException::SALT_LENGTH_HIGH - if the data length exceeds C INT_MAX

KDF::derive($password)

Description: An abstract method to derive the key from the password.

The derive abstract method has to be used in all subclasses to derive the key from the supplied password. If the derivation fails, it must throw KDFException.

Parameters

password : string - the password

Return value

string: Derived key.

Throws

The implementing method can throw KDFException with code

  • KDFException::DERIVATION_FAILED - the derivation failed
  • KDFException::PASSWORD_LENGTH_INVALID - if the password length exceeds C INT_MAX

KDF::getLength()

Description: Returns a length of the derived key.

This method returns a lenght of the key that will be or was derived by the KDF::derive.

Parameters

This method has no parameters.

Throws

This method does not throw any exception.

Return value

int: The lenght of the derived key.

KDF::getSalt()

Description: Returns salt for the key derivation.

This method returns salt string that will be used when deriving a key using KDF::derive.

Parameters

This method has no parameters.

Throws

This method does not throw any exception.

Return value

string: The salt.

KDF::setLength($length)

Description: Sets a length for the derived key.

This method sets a length that will be the string length of the derived key.

Parameters

length : int - key length

Throws

It can throw KDFException with code

  • KDFException::KEY_LENGTH_LOW - if key length is less than 0
  • KDFException::KEY_LENGTH_HIGH - if key length is more than C INT_MAX value
Return value

bool: true if the key length was set succesfully

KDF::setSalt($salt)

Description: Sets salt for the key derivation.

This method sets salt that will be used when deriving key using KDF::derive.

Parameters

salt : string - salt for the key derivation

Throws

It can throw KDFException with code

  • KDFException::SALT_LENGTH_HIGH - if the salt length is more than C INT_MAX
Return value

bool: true if the salt was set succesfully