LoadPfxFile Takes a Long Time to Load?

Question:

I’m using the LoadPfxFile method of the cert object and it takes about 4 or 5 seconds in load the PFX certificate.
On the other hand, if I sign the document using an installed certificate, it’s instantaneous.
Why does LoadPfxFile take so much time? Is there a way to reduce the loadPfxFile time?

Answer:

When a password is used to open a .pfx (.p12) file, the password is transformed to a binary key using PBKDF2 as a key derivation function. See https://datatracker.ietf.org/doc/html/rfc7292#appendix-B

The iteration count when deriving a key from a password for PFX (Personal Information Exchange) serves as a security measure to make key derivation more time-consuming and resistant to brute-force attacks.

PFX is a file format used to store a private key and its associated certificate(s). When encrypting the private key with a password, the password is not directly used as the encryption key. Instead, a key derivation function (KDF) is applied to the password to generate a stronger encryption key.

The iteration count refers to the number of times the KDF algorithm is applied in the key derivation process. Each iteration involves executing the KDF algorithm, which typically includes one or more computationally intensive operations such as hashing or HMAC. By increasing the iteration count, the key derivation process becomes slower and more resource-intensive.

The purpose of the iteration count is to increase the time and effort required to derive the key from the password. This slows down attackers attempting to guess the password through brute-force or dictionary attacks. With a higher iteration count, each password guess takes longer to process, making it less feasible for an attacker to try a large number of passwords within a reasonable timeframe.

A higher iteration count provides a stronger defense against offline attacks where an attacker has access to the encrypted PFX file and can attempt to derive the key offline using various passwords. It increases the computational cost for the attacker, making it more difficult to guess the correct password and derive the encryption key.

Note:

If you are using an older version of Chilkat, try updating to the latest version to see if there is any improvement. However, it may be that the iteration count is too large and it’s simply the case that the key derivation is intended to take longer. Also, one should realize this strategy of using an iteration count + hash algorithm will result in vastly different run times depending on the CPU power of a given computer.