>Just for something quick and easy, I took the return value of sys(2007, "password") (the checksum of the password) and stored it to the user table. Then when the user logs in, I compare the checksum of the password they entered to what’s in the user table. Now this does have a drawback of not being able to recreate the users password if they forget it (maybe that’s not a drawback) but it is easy and somewhat secure.


I checked out sys(2027) recently and I believe it returns a 16 bit integer. This means that there is one chance in 64K that a user can type a random-string and get in. Not bad but something to bear in mind.

Attached below is a simple cryptographic routine that I wrote. It's reversible so that you can regenerate the password from the encrypted string (if you pass the right seed).


***********************************************************************
* FUNCTION EncodeRS() LIBRARY FPRS\PROGS\
***********************************************************************
* Purpose.....: Returns a character string which is an encrypted version
* of the character string tcString.
* Parameters..: tcString
* tnSeed
* Returns.....: character -- encoded string
* Notes.......: The input string is stripped of leading and trailing blanks
* and then padded with blanks to a length which is divisible by 4
* The encoded string consists of the characters A through P
* with a blank inserted after every 8 characters.
* Examples....: lcEncodedString = EncodeRS(lcString)
* Calls.......: BintoNib()
* Project.....: Rodes Software FoxPro Utilities
* Version.....: 1999
* Platform....: Visual FoxPro 5.0
* Author......: Peter Robinson
* Copyright...: (c) Rodes Software, 1999
* Created.....: 1999.02.10
* History.....:
**********************************************************************

lparameter tcString, tnSeed

local lcString && Input string with leading & trailing blanks removed
local lnPad && number of spaces to add to the end of tcString
local lnW && pointer to first byte of each word (4 bytes)
local lnWord && bit value of each word
local lcCrypto && encoded string

if type("tcString") <> "C" or empty(tcString)
return ""
endif

if type("tnSeed") <> "N" or tnSeed = 0
return ""
endif

lcString = alltrim(tcString)

lnPad = len(lcString) % 4
if lnPad <> 0
lcString = lcString + space(4-lnPad)
endif

rand(tnSeed)

lcCrypto = ""

for lnW = 1 to len(lcString) - 1 step 4
lnWord = ctobin(substr(lcString,lnW,4))
lnWord = bitxor(lnWord,rand()*2147483647)
lcCrypto = lcCrypto + BintoNib(lnWord) + " "
endfor

return lcCrypto



***********************************************************************
* FUNCTION DecodeRS() LIBRARY FPRS\PROGS\
***********************************************************************
* Purpose.....: Returns a character string which is the plain text
* translation of the encoded string tcString.
* Parameters..: tcString
* tnSeed
* Returns.....: character -- plain text
* Notes.......: The encoded string consists of the characters A through P
* with a blank inserted after every four characters.
* Examples....: lcPlainText = DecodeRS(lcEncodedString)
* Calls.......: NibtoBin()
* Project.....: Rodes Software FoxPro Utilities
* Version.....: 1999
* Platform....: Visual FoxPro 5.0
* Author......: Peter Robinson
* Copyright...: (c) Rodes Software, 1999
* Created.....: 1999.02.10
* History.....:
**********************************************************************

lparameter tcString, tnSeed

local lcString && Input string with blanks stripped out
local lnW && pointer to beginning of each word (8 nibbles)
local lnWord && bit value of each word
local lcPlain && decoded string

if type("tcString") <> "C" or empty(tcString)
return ""
endif

if type("tnSeed") <> "N" or tnSeed = 0
return ""
endif

lcString = chrtran(tcString," ","")

if len(lcString) % 8 <> 0
return ""
endif

rand(tnSeed)

lcPlain = ""

for lnW = 1 to len(lcString) - 1 step 8
lnWord = NibtoBin(substr(lcString,lnW,8))
lnWord = bitxor(lnWord,rand()*2147483647)
lcPlain = lcPlain + bintoc(lnWord)
endfor

return lcPlain



***********************************************************************
* FUNCTION BintoNib()
***********************************************************************
* Purpose.....: Convert a signed integer to the equivalent in nibbles
* (half-bytes) where 0000 = A, 0001 = B, ..., 1111 = P
* Parameters..: tnWord
* Returns.....: char -- 8
* Notes.......: Bit patterns:
* 15 = 00001111
* 240 = 11110000
* 255 = 00000000 00000000 00000000 11111111
* 65280 = 00000000 00000000 11111111 00000000
* 16711680 = 00000000 11111111 00000000 00000000
*
* Examples....: Following expressions produce a true value:
* BintoNib(-2147483648) = "IAAAAAAA" && -2^31
* BintoNib(-1) = "PPPPPPPP"
* BintoNib(0) = "AAAAAAAA"
* BintoNib(1) = "AAAAAAAB"
* BintoNib(2147483647) = "HPPPPPPP" && 2^31 - 1
*
* Calls.......: none
* Created.....: 1999.02.10
* History.....:
**********************************************************************

LPARAMETER tnWord

local lnByte1, lnByte2, lnByte3, lnByte4

if type("tnWord") <> "N"
return spaces(8)
endif

lnByte1 = bitrshift(tnWord,24)
lnByte2 = int(bitand(tnWord,16711680) / 65536)
lnByte3 = int(bitand(tnWord,65280) / 256 )
lnByte4 = bitand(tnWord,255)

return chr(65 + bitand(lnByte1,240)/16 ) ;
+ chr(65 + bitand(lnByte1,15) ) ;
+ chr(65 + bitand(lnByte2,240)/16 ) ;
+ chr(65 + bitand(lnByte2,15) ) ;
+ chr(65 + bitand(lnByte3,240)/16 ) ;
+ chr(65 + bitand(lnByte3,15) ) ;
+ chr(65 + bitand(lnByte4,240)/16 ) ;
+ chr(65 + bitand(lnByte4,15) )



***********************************************************************
* FUNCTION NibtoBin()
***********************************************************************
* Purpose.....: Convert a nibble string (half-bytes--characters A-P)
* to the equivalent signed integer
* where 0000 = A, 0001 = B, ..., 1111 = P
* Parameters..: tnWord
* Returns.....: char -- 8
* Notes.......: Bit patterns:
* 16 = 00000000 00000000 00000000 00010000
* 256 = 00000000 00000000 00000001 00000000
* 4096 = 00000000 00000000 00010000 00000000
* 65536 = 00000000 00000001 00000000 00000000
* 1048576 = 00000000 00010000 00000000 00000000
* 16777216 = 00000001 00000000 00000000 00000000
* 2147483647 = 01111111 11111111 11111111 11111111 = 2^31-1
*
* Examples....: Following expressions produce a true value:
* NibtoBin("IAAAAAAA") = -2147483648
* NibtoBin("PPPPPPPP") = -1
* NibtoBin("AAAAAAAA") = 0
* NibtoBin("AAAAAAAB") = 1
* NibtoBin("HPPPPPPP") = 2147483647
*
* Calls.......: none
* Created.....: 1999.02.10
* History.....:
**********************************************************************

lparameter tcNibbles

local lcNibble && input string padded on left with "A"
local lnNibble1 && numeric value of first nibble
local lnRest && numeric value of remaining nibbles

if type("tcNibbles") <> "C" or empty(tcNibbles)
return 0
endif

lcNibbles = right("AAAAAAAA"+upper(alltrim(tcNibbles)),8)

lnNibble1 = asc(substr(lcNibbles,1,1)) - 65
** avoid setting sign bit

lnRest = (asc(substr(lcNibbles,2,1)) - 65) * 16777216 ;
+ (asc(substr(lcNibbles,3,1)) - 65) * 1048576 ;
+ (asc(substr(lcNibbles,4,1)) - 65) * 65536 ;
+ (asc(substr(lcNibbles,5,1)) - 65) * 4096 ;
+ (asc(substr(lcNibbles,6,1)) - 65) * 256 ;
+ (asc(substr(lcNibbles,7,1)) - 65) * 16 ;
+ (asc(substr(lcNibbles,8,1)) - 65)

return bitor(bitlshift(lnNibble1,28),lnRest)