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Source Technologies, LLC ST9630 Secure MICR Printer User’s Guide
40
Decryption Commands
Decryption requires printer processing overhead. In our testing encrypted printer data
steams near or below 100K bytes per page do not seem to affect printer speed in term of
pages per minute or first page out timings. Some testing done with print files from 500K
to 1 Meg per page revealed up to a 30% degradation in speed. It is therefore
recommended the encryption be reserved for the confidential portions of the data when
large file sizes are anticipated.
Set DES Decryption Key Command – &%STSETDESKEY<16 Hex Characters>$
The command requires a MICR Password Command be sent prior to the Key
Command. The Key Command could itself be encrypted and then decrypted in the
printer. The command requires the key data be in a double-byte hex format. The 8 byte
value must be converted to the 16 byte format. The only values that can be contained in
the 16 command bytes are 0 through 9, A through F. Alpha key characters can be upper
or lower case. Command characters must be upper case. Here is an example of a valid
key command - &%STSETDESKEY5f00FF7E3DA938eb$. The key value remains in the
printer until another key command is received. Printer power cycles and printer reset
commands do not affect the key value.
The dollar sign ($) is the command terminator and is required.
Set AES Decryption Key Command – &%STSETAESKEY<32 Hex Characters>$
The command also requires a MICR Password Command be sent prior to the Key
Command.
The key data is similar to DES, but is twice in length with 32 Hex character format
representing the 16 byte or 128-bit key value.
Turn DES Decryption ON – &%STDON$
Turn AES Decryption ON – &%STAON$
All data following the $ command terminator will be decrypted using the current key
value stored in the printer and the DES or AES algorithm. Decryption continues until a
Decryption OFF command is received, a printer panel reset occurs, or printer power is
cycled. Printer software language resets do not stop decryption.
Turn DES Decryption OFF – &%STDOFF$
Turn AES Decryption OFF – &%STAOFF$
The OFF command resides within the encrypted data, and must also be encrypted. The
OFF occurs after an 8-byte block (DES) or 16-byte block (AES) is received and
decrypted. The last block containing the OFF should either have the command right
justified or padded out to the block boundary. Any padding bytes after the $ command
terminator will be discarded.
MICR Features | 6