>>>>Regarding Mike Gagnon's suggestion, remember that you have already a series of integer values, not of 32-bit integers, but of 8-bit integers. That's what a string is. To hold 250 different logical values, CEILING(250 / 8) = 32 characters would be enough, and a string like yours "YYYNYYNN" could be represented as a single CHR(236).
>>>
>>>Hi Antonio,
>>>
>>>Thank you for your suggestions. As far as your explanation of 250 logical values and 32-bit integers, I hang my head in shame. I don't understand it off the typed message (lack of formal computer education shows). But I will read it again and hopefully get it, at some point. Thank you.
>>
>>Dmitry, you'll see that it's not that complicated.
>>
>>Unfortunately, VFP does not have a native representation of binary numbers, but the functions that Thomas referred you to are what you need to question and set a bitmap of this sort, and that you can even incorporate in SQL queries if you want to.
>
>To encode() and decode() as Antonio suggests, it creates a binary string:
>

seedRand(0)
>lcString = SPACE(0)
>FOR lnI = 1 TO 250
>    lcString = lcString + IIF(ROUND((getRand() * 100), 0) % 2 = 1, "Y", "N")
>NEXT
>
>CLEAR
>lcEnc = encode(lcString)
>lcDec = decode(lcEnc)
>? "Encoded, do they match?", (lcDec = lcString)
>
>lcEnc = encrypt(encode(lcString))
>lcDec = decode(decrypt(lcEnc))
>? "Encrypted and encoded, do they match?", (lcDec = lcString)
>
>
>
>
>FUNCTION encode
>LPARAMETERS tcString
>LOCAL lnI, lnBit, lnOffset, lcChar, lnBinChar, lcString
>
>    * Make sure our string is an even multiple of 8 (to round up to the nearest byte boundary)
>    lnString = LEN(tcString)
>    IF LEN(tcString) % 8 != 0
>        tcString = tcString + SPACE(8 - (LEN(tcString) % 8))
>    ENDIF
>
>    * Create our output string
>    lcString = CHR(lnString) + REPLICATE(CHR(0), LEN(tcString) / 4)
>
>    * Process through each byte of the input string
>    lnOffset = 2
>    FOR lnI = 1 TO LEN(tcString) STEP 8
>        lnBinChar   = ASC(SUBSTR(lcString, lnOffset, 1))
>        lnBit       = 128
>        FOR lnJ = 0 TO 7
>            lcChar      = SUBSTR(tcString, lnI + lnJ, 1)
>            lnBinChar   = BITOR(lnBinChar, IIF(lcChar $ "Yy", lnBit, 0))
>            lnBit       = lnBit / 2
>        NEXT
>        lcString = STUFF(lcString, lnOffset, 1, CHR(lnBinChar))
>        lnOffset = lnOffset + 1
>    NEXT
>    RETURN lcString
>
>
>
>
>FUNCTION decode
>LPARAMETERS tcString
>LOCAL lcString
>
>    * Extract the total output string length
>    lcString    = SPACE(ASC(SUBSTR(tcString, 1, 1)))
>    lnOffset    = 2
>    FOR lnI = 1 TO LEN(lcString)
>        lcBinChar   = ASC(SUBSTR(tcString, lnOffset, 1))
>        lnBit       = 128
>        FOR lnJ = 0 TO 7
>            lcString    = STUFF(lcString, 1 + ((lnI - 1) * 8) + lnJ, 1, IIF(BITAND(lcBinChar, lnBit) != 0, "Y", "N"))
>            lnBit       = lnBit / 2
>        NEXT
>        lnOffset = lnOffset + 1
>    NEXT
>    RETURN lcString
>
>
>
>
>FUNCTION encrypt
>LPARAMETERS tcString
>LOCAL lcString
>
>    seedRand(0)
>    lcString = SPACE(0)
>    FOR lnI = 1 TO LEN(tcString)
>        lnRand      = ROUND(getRand() * 255.0, 0)
>        lcChar      = SUBSTR(tcString, lnI, 1)
>        lcChar      = CHR((ASC(lcChar) + lnRand) % 255)
>        lcString    = lcString + lcChar
>    NEXT
>    RETURN lcString
>
>
>
>
>FUNCTION decrypt
>LPARAMETERS tcString
>LOCAL lcString
>
>    seedRand(0)
>    lcString = SPACE(0)
>    FOR lnI = 1 TO LEN(tcString)
>        lnRand      = ROUND(getRand() * 255.0, 0)
>        lcChar      = SUBSTR(tcString, lnI, 1)
>        lcString    = lcString + CHR((ASC(lcChar) + 255 - lnRand) % 255)
>    NEXT
>    RETURN lcString
>
>
>
>
>FUNCTION seedRand
>LPARAMETERS tnSeed
>
>    DECLARE INTEGER srand IN msvcr71.dll as cSrand INTEGER nSeed
>    DECLARE INTEGER rand  IN msvcr71.dll AS cRand
>    cSrand(tnSeed)
>
>
>
>
>FUNCTION getRand
>LOCAL lnRand
>
>    RETURN cRand() / 32767.0
>

Hi Rick,

You probably meant this message for me and sent it to Antonio. Anyway, thank you for the code. I will review it, as an academic exercise and for learning.
However, as far as actually implementing this in my application, I chose to use the Cipher() function, using the field PK as a seed. So far, in testing (on my computer) everything works pretty well.
Just as FYI, I have this field (with "Y"s and "N"s) open (uncrypted) for 20+ years and not one time anybody knew or noticed it. The users don't see the data and the IT do not care how it works, as long as it works.
I wanted to encrypt the field more because I felt it was not right, rather than the program was ever hacked.