Supported Cryptographic Operations for PKCS#11

CADP for C PKCS#11 allows you to implement data privacy, confidentiality, and integrity in a simple, scalable, and secure manner.

The operations supported are as follows:

To encrypt or decrypt with a block algorithm, it must be possible to divide the plaintext value into full blocks of a specific size. (In the case of AES, the block size is sixteen bytes).

If the plaintext length is not a multiple of the algorithm’s block size, padding is used to fill the remainder of the last block. If the length of the plaintext value is a multiple of the block size, padding is used to fill an additional, trailing block.

This additional block indicates that the padding is not present in the preceding blocks. The ciphertext is greater than the original plaintext value, regardless of the algorithm used to encrypt the data.

The following table illustrates how this is true for the AES algorithms.

Asymmetric algorithms, such as RSA, can be up to an order of magnitude slower than symmetric algorithms.

When using RSA keys to encrypt data, the ciphertext is always the size of the key. If your RSA key is 2048 bits (or 256 bytes), then the ciphertext is also 256 bytes. For example, if you use a 2048-bit RSA key, the maximum data size that you can encrypt with that key is 245 bytes.

The speed and size issues make public key cryptography impractical for encrypting data. Hence, it is recommended to use symmetric key algorithms to encrypt your data.

Modes of Operation

If you are using a block cipher with AES, decide whether you want to use the algorithm in Electronic Code Book (ECB) mode, or Cipher-Block Chaining (CBC) mode.

• In ECB mode, each block is encrypted separately, through the same procedure. Thus, two identical plaintext blocks encrypt to the same ciphertext and any data patterns in the plaintext can be detected in the encrypted data.

• In CBC mode, the first block is XORed with an initialization vector before being encrypted. All subsequent plaintext blocks are XORed with the previous ciphertext block before being encrypted. This dependency makes it more difficult for an attacker to swap blocks, because blocks must be decrypted in the same order in which they were encrypted to produce the original plaintext.
  When the same key and different IVs are used, identical plaintexts are guaranteed to have different ciphertexts.

It is recommended to use CBC mode, unless you have a compelling reason to use ECB mode.

Initialization Vectors

An initialization vector (IV) is a sequence of random bytes appended to the front of the plaintext before encryption. Use of a unique IV eliminates the possibility that the initial ciphertext block is the same for any two encryption operations of the same plaintext that use the same key. In the CipherTrust Manager environment, IVs are only used by block ciphers in CBC mode. The size of the IV depends on the algorithm; AES uses a sixteen byte IV. The CipherTrust Manager can generate random IVs, or user can supply own IV.

The eight byte IV requires sixteen characters; likewise, a sixteen byte IV requires thirty-two characters. Sometimes, the examples in this documentation show impractical IVs for the sake of simplicity, for example 112233445566.... Make sure that IV is sufficiently complex, and if supplying own IV for anything other than data migration, it is crucial to remember the IV supplied.

To ensure a unique ciphertext during data migration, it is required to apply IVs at the field–level and not the column–level.

In general, it is recommended to use symmetric (one of the following) block ciphers to encrypt data in the CipherTrust Manager environment: AES or FPE. Out of the symmetric block ciphers, it is further recommended to use AES because it performs better and is considered to be more secure than others. To preserve the formatting of data, use FPE algorithm.

Supported Algorithms

The supported algorithms are:

• AES

• AES/GCM

• HMAC-SHA

• RSA

• FPE

• FF1

AES

AES/GCM

HMAC-SHA

RSA

FPE