TR-31 optional block data

DA optional block

The DA optional block is a standard optional block used to define derivations allowed for derivation keys. That is to say, it allows the user to set which types of keys a derivation key can create. The DA optional block can only be set in a TR-31 key block with TR-31 key usage B3, otherwise it is not allowed. This block will contain one or more sets of key attributes, up to a maximum of 49 sets, contained in 5 byte ASCII strings. Each string will contain key usage, algorithm, TR-31 mode of key use, and exportability. For example, imagine you want to limit your B3 TR-31 key token to only generate PIN encryption keys, that use the TDEA algorithm, and that are only allowed to encrypt, and that are exportable. For these attributes and purposes, you would place the following string into your DA optional block:

P0TEE

Here are a few other examples and their breakdowns:

P0TDE (P0, T, D, E)

• Only the following derivation is allowed: PIN Encryption key usage P0, TDEA algorithm, Decrypt only TR-31 mode of key use, Exportable

P0TEED0AEN (P0, T, E, E, D0, A, E, N)

• First Derivation allowed: PIN Encryption key usage P0, TDEA algorithm, Encrypt only mode of use, Exportable
• Second Derivation allowed: Symmetric Data Encryption key usage D0, AES algorithm, Encrypt Only mode of use, Not Exportable

IBM-defined optional block

IBM optional block internal controls

The IBM optional block with TLV ID ’02’ (X’3032’) consists of 12 bytes that are represented using 24 hex ASCII bytes. The 12 bytes are built as follows:

• The first four bytes are general bytes applicable to all optional blocks.
• The second four bytes are type specific and only used for certain TR-31 key usages. Currently only the first byte of this set is used. These bytes will be set to zero if they are unused.
  Note: For CCA 8.1, these controls (the controls specified in the second four bytes) are not added, and the first bit of this byte (bit 32) is set to 1 to indicate that there are NO CONTROLS ADDED YET. Anything else that is in the byte is ignored if bit 32 is set to 1. When further controls are added, this should be set to 0 to indicate that this byte information should be used.
• The last four bytes are reserved for future use and should be set to 0.

The first byte (offset 12) with bit fields 0 through 7 set as 00000ceD is a general flag byte applicable for all optional blocks. The flags are as follows:

• Bit 0: reserved, 0
• Bit 1: reserved, 0
• Bit 2: reserved, 0
• Bit 3: reserved, 0
• Bit 4: reserved, 0
• Bit 5: 1 = Compliance Tag (see c in 00000ceD)
• Bit 6: 1 = CPACF export bit control (see e in 00000ceD)
• Bit 7: 1 = Only usable in DK services, DKPINOP/KUF equivalent (see D in 00000ceD)

The following three bytes are used as the KDF indicator and should be set as follows:

• Second byte (offset 13): 0x00
• Third byte (offset 14): 0x00
• Fourth byte (offset 15), KDF indicator:
  • 0x00: No KDF / comp-tag indicator
  • 0x04: Comp-tag KDF for TR-31