Crypto.DecryptBuffer

This command decrypts a variable length buffer given in the Buffer parameter using the SkipJack algorithm. If KeyIndex is set to 0x00, KeyValue will be used as encryption key. Otherwise, KeyIndex is interpreted as the index of the corresponding entry in the internal key list. KeyIndex = 0x01 denotes configuration value 0x81, KeyIndex = 0x02 denotes configuration value 0x82, etc.

The value returned in the InitialVector variable is necessary for CBC encryption. If large amounts of data must be encrypted, this command has to be called more than once. In this case, the returned InitialVector variable of call i of the command has to be specified as the InitialVector parameter of call i+1.

Properties

Command code: 0x0203
Command timeout: 100 ms
Possible status codes: General status codes, Crypto.CrptErrAuth, Crypto.CrptErrKeyNotFound

Parameters (request frame)

Name

Type/Size

Description

KeyIndex

Integer (8 bits)

Index of key to use to decrypt data. KeyIndex must be set to 0x00 if a user-defined key, specified in the KeyValue parameter, should be used for decryption.

Optional field, condition: KeyIndex == 0x0

KeyValue

Raw data (length 10 Bytes)

If KeyIndex is set to 0x00, this value specifies a user-defined decryption key.

InitialVector

Raw data (length 8 Bytes)

Initial vector (IV) used for decryption.

Length of Buffer

Integer (8 bits)

Length of Buffer in bytes

Buffer

Raw data

Data buffer to decrypt.

Returned values (response frame)

Name	Type/Size	Description
NextInitialVector	Raw data (length 8 Bytes)	Initial vector to be used as InitialVector parameter in the next call of this command.
Length of UnencryptedBuffer	Integer (8 bits)	Length of UnencryptedBuffer in bytes
UnencryptedBuffer	Raw data	Unencrypted buffer after decryption.