Help in DES decoding issue

Hi,

  I'm facing issue in DES decoding for few number value. Basically, The main objective is to encrypt the test case number and the test result and put it in a file then decode it later. I have written below procedure to do the above task.

Issues - Few numbers are not getting decoded properly. Ex "2" or "6". If I run the procedure using the argument value as follows

  %tst_rslt_encode 11111111 4.1.4.1 PASS

and when I pass 4.1.4.2 or 4.1.4.6, the decode fails.

Am I doing mistake in reading the encrypted data from file ? Btw, the above test case works if I decode directly without storing it in a file.

Any suggestions would be greatly appreciated.

Script :-

package require des

proc tst_rslt_encode {key test_case tst_status} {

    # Assign the key value and set the file locations
    set t_key ""
    set master_key [string trim $key]   

    # Find out the 64 bytes total key using test case and master key
    set t_key [get_ttl_key $test_case $master_key]
   
    # set the file location for storing the encrypted output    
    set key_file    "D:\\test_file.txt"
    set result_file "D:\\test_output.txt"

    # Insure a file exists before reading
    if ![file exists $key_file] {
         set cr_file [open $key_file w+]
         close  $cr_file     
    }   

    # Encode the test case number using master key and append the file

    set key_cipher [DES::des -mode ecb -dir encrypt -key $master_key $dyn_key]
     
    if [catch {set keyFd [open $key_file a]} errmsg] {
        puts "Unable to open file $key_file for write\n$errmsg"
        return
    }
    puts $keyFd $key_cipher

    close $keyFd
   
    # Now encode the result using total key and append the result file
    if [catch {set resFd [open $result_file a+]} errmsg] {
        puts "Unable to open file $result_file for write\n$errmsg"
        return
    }

    set status [string trim $tst_status]     
    set test_cipher [DES::des -mode ecb -dir encrypt -key $t_key $status]
    puts "Here is the output of test_cipher :$test_cipher"
    puts $resFd $test_cipher
    close $resFd

    # Now decode the test case and test results
  
    set xfd [open $result_file r]
    set outFd [open $key_file r]
    while {[gets $xfd data] != -1 && [gets $outFd data1] != -1 } {          
           set tst_cs [string trim $data]
           set tst_rslt [string trim $data1]
           set tc_plain [DES::des -mode ecb -dir decrypt -key $master_key $tst_rslt]
           # find out the total key
           set t_key [get_ttl_key $tc_plain $master_key]          
           set rslt_plain [DES::des -mode ecb -dir decrypt -key $t_key $tst_cs]         
           puts "This should be the output after decode :$tc_plain $rslt_plain"                   
    }
    close $xfd
    close $outFd
    return
}

proc get_ttl_key {tst_case mst_key} {

    # Remove the "." from test case  
    regsub -all "\\." $tst_case "" dyn_key
    set dyn_key [string trim $dyn_key]

    # Find out the 64 bytes total key using test case and master key
    set mkey_len [expr 8 - [string length $dyn_key]]
    set ms_key [string range $master_key 0 [expr $mkey_len - 1]]
    append tt_key $dyn_key $ms_key   
    set tt_key [string trim $tt_key]  

    return $tt_key

}