KeySizeBits Method

KeySizeBits(PivAlgorithm)

The size of a key, in bits, of the given algorithm.

C#

public static int KeySizeBits(this PivAlgorithm algorithm)

Parameters

Type	Name	Description
PivAlgorithm	algorithm	The algorithm name to check.

Returns

System.Int32

An int, the size, in bits, of a key of the given algorithm.

Remarks

The PivAlgorithm enum specifies algorithm and key size for RSA and ECC. If you have a variable of type PivAlgorithm, use this extension to get the bit size out.

For example, suppose you obtain a public key from storage, and have a PivPublicKey object. Maybe your code performs different tasks based on the key size (e.g. use SHA-256 or SHA-384, or build a buffer for signing). You can look at the Algorithm property to learn the algorithm and key size. However, if all you want is the key size, use this extension:

   PivPublicKey publicKey = SomeClass.GetPublicKey(someSearchParam);
   byte[] buffer = new byte[publicKey.Algorithm.KeySizeBits() / 8];

This will return the following values for each value of PivAlgorithm.

    Rsa1024    1024
    Rsa2048    2048
    Rsa3072    3072
    Rsa4096    4096
    EccP256     256
    EccP384     384
    TripleDes   192
    Pin          64
    None          0

Note that a Triple-DES key is made up of three DES keys, and each DES key is 8 bytes (64 bits). However, because there are 8 "parity bits" in each DES key, the actual key strength of a DES key is 56 bits. That means the actual key strength of a Triple-DES key is 168 bits. In addition, because of certain attacks, it is possible to reduce the strength of a Triple-DES key to 112 bits (it takes the equivalent of a 112-bit brute-force attack to break a Triple-DES key). Nonetheless, this extension will return 192 as the key length, in bits, of a Triple-DES key.

A PIN or PUK is 6 to 8 bytes long. Hence, the maximum size, in bits, of a PivAlgorithm.Pin is 64.