使用MD5算法加密VFP数据
我们的VFP数据太开放了些，用Excel随便打开一个DBF表，里面的数据就一览无遗。如果数据是比较敏感的话，可就坏事了。例如：我的数据录入员的程序登录密码是放在一个VFP表里，经过加密，就算用Excel打开DBF表，也是看不到密码的。从一个随书资料盘上见到此段代码，供大家参考。
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********md5.prg**********
FUNCTION LShift(lvalue, iShiftBits)
IF iShiftBits = 0
RETURN lvalue
ELSE
IF iShiftBits = 31
IF BITAND(lvalue , 1)<>0
RETURN 0x80000000
ELSE
RETURN 0
ENDIF
ENDIF
ENDIF
IF BITAND(lvalue , m_l2Power(31 - iShiftBits))<>0
RETURN BITOR( (BITAND(lvalue , m_lOnBits(31 - (iShiftBits + 1))) * m_l2Power(iShiftBits)) , 0x80000000)
ELSE
RETURN (BITAND(lvalue , m_lOnBits(31 - iShiftBits)) * m_l2Power(iShiftBits))
ENDIF
ENDFUNC
FUNCTION RShift(lvalue, iShiftBits)
IF iShiftBits = 0
RETURN lvalue
ELSE
IF iShiftBits = 31
IF BITAND(lvalue , 0x80000000)
RETURN 1
ELSE
RETURN 0
ENDIF
ENDIF
ENDIF
RShift2 = INT(BITAND(lvalue , 0x7FFFFFFE) / m_l2Power(iShiftBits))
IF BITAND(lvalue , 0x80000000)<>0
RShift2 =BITOR (RShift2 , INT(0x40000000 / m_l2Power(iShiftBits - 1)))
ENDIF
RETURN RShift2
ENDFUNC
FUNCTION RotateLeft(lvalue, iShiftBits)
RETURN BITOR(LShift(lvalue, iShiftBits) ,RShift(lvalue, (32 - iShiftBits)))
ENDFUNC
FUNCTION AddUnsigned(lX, lY)
lX8 = BITAND(lX , 0x80000000)
lY8 = BITAND(lY , 0x80000000)
lX4 = BITAND(lX , 0x40000000)
lY4 = BITAND(lY , 0x40000000)
lResult = BITAND(lX , 0x3FFFFFFF) + BITAND(lY , 0x3FFFFFFF)
IF BITAND(lX4 , lY4)<> 0
lResult = BITXOR(BITXOR(BITXOR(lResult , 0x80000000) , lX8) , lY8)
ELSE
IF BITOR(lX4 , lY4)<> 0
IF BITAND(lResult , 0x40000000)<> 0
lResult = BITXOR(BITXOR(BITXOR(lResult , 0xC0000000) , lX8) , lY8)
ELSE
lResult = BITXOR(BITXOR(BITXOR(lResult , 0x40000000) , lX8) , lY8)
ENDIF
ELSE
lResult = BITXOR(BITXOR( lResult , lX8) , lY8)
ENDIF
ENDIF
RETURN lResult
ENDFUN
C
FUNCTION md5_F(x, y, z)
RETURN BITOR(BITAND(x , y) , BITAND(BITNOT(x) , z))
ENDFUNC
FUNCTION md5_G(x, y, z)
RETURN BITOR(BITAND(x , z) , BITAND(y , BITNOT(z)))
ENDFUNC
FUNCTION md5_H(x, y, z)
RETURN BITXOR(BITXOR(x , y) , z)
ENDFUNC
FUNCTION md5_I(x, y, z)
RETURN BITXOR(y , BITOR(x , BITNOT(z)))
ENDFUNC
PROCEDURE md5_FF(a, b, c, d, x, s, ac)
a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_F(b, c, d), x), ac))
a = RotateLeft(a, s)
a = AddUnsigned(a, b)
ENDPROC
PROCEDURE md5_GG(a, b, c, d, x, s, ac)
a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_G(b, c, d), x), ac))
a = RotateLeft(a, s)
a = AddUnsigned(a, b)
ENDPROC
PROCEDURE md5_HH(a, b, c, d, x, s, ac)
a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_H(b, c, d), x), ac))
a = RotateLeft(a, s)
a = AddUnsigned(a, b)
ENDPROC
PROCEDURE md5_II(a, b, c, d, x, s, ac)
a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_I(b, c, d), x), ac))
a = RotateLeft(a, s)
a = AddUnsigned(a, b)
ENDPROC
FUNCTION Hex(lByte)
x=’’
DO WHILE lByte>0
IF lByte>=16
y=lByte
ELSE
y=lByte
ENDIF
IF y<10 .and. y>=0
x=STR(y,1)+x
ELSE
x=CHR(65+y-10)+x
ENDIF
lByte=(lByte-y)/16
ENDDO
RETURN x
ENDFUNC
FUNCTION WordToHex(lvalue)
lResult=’’
FOR lCount = 0 TO 3
lByte = BITAND(RShift(lvalue, lCount * BITS_TO_A_BYTE) , m_lOnBits(BITS_TO_A_BYTE ))
lResult = lResult + RIGHT("0" + Hex(lByte), 2)
ENDFOR
RETURN lResult
ENDFUNC
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*****设置错误处理程序，因Visual FoxPro程序本身所限，对大数的处理能力不够
ON ERROR do err_treat
FOR k = 1 TO ;lNumberOfWords STEP 16
AA = a
BB = b
CC = c
DD = d
DO md5_FF WITH a, b, c, d, x(k + 0), S11, 0xD76AA478
DO md5_FF WITH d, a, b, c, x(k + 1), S12, 0xE8C7B756
DO md5_FF WITH c, d, a, b, x(k + 2), S13, 0x242070DB
DO md5_FF WITH b, c, d, a, x(k + 3), S14, 0xC1BDCEEE
DO md5_FF WITH a, b, c, d, x(k + 4), S11, 0xF57C0FAF
DO md5_FF WITH d, a, b, c, x(k + 5), S12, 0x4787C62A
DO md5_FF WITH c, d, a, b, x(k + 6), S13, 0xA8304613
DO md5_FF WITH b, c, d, a, x(k + 7), S14, 0xFD469501
DO md5_FF WITH a, b, c, d, x(k + 8), S11, 0x698098D8
DO md5_FF WITH d, a, b, c , x(k + 9), S12, 0x8B44F7AF
DO md5_FF WITH c, d, a, b, x(k + 10), S13, 0xFFFF5BB1
DO md5_FF WITH b, c, d, a, x(k + 11), S14, 0x895CD7BE
DO md5_FF WITH a, b, c, d, x(k + 12), S11, 0x6B901122
DO md5_FF WITH d, a, b, c, x(k + 13), S12, 0xFD987193
DO md5_FF WITH c, d, a, b, x(k + 14), S13, 0xA679438E
DO md5_FF WITH b, c, d, a, x(k + 15), S14, 0x49B40821
DO md5_GG WITH a, b, c, d, x(k + 1), S21, 0xF61E2562
DO md5_GG WITH d, a, b, c, x(k + 6), S22, 0xC040B340
DO md5_GG WITH c, d, a, b, x(k + 11), S23, 0x265E5A51
DO md5_GG WITH b, c, d, a, x(k + 0), S24, 0xE9B6C7AA
DO md5_GG WITH a, b, c, d, x(k + 5), S21, 0xD62F105D
DO md5_GG WITH d, a, b, c, x(k + 10), S22, 0x2441453
DO md5_GG WITH c, d, a, b, x(k + 15), S23, 0xD8A1E681
DO md5_GG WITH b, c, d, a, x(k + 4), S24, 0xE7D3FBC8
DO md5_GG WITH a, b, c, d, x(k + 9), S21,&n bsp;0x21E1CDE6
DO md5_GG WITH d, a, b, c, x(k + 14), S22, 0xC33707D6
DO md5_GG WITH c, d, a, b, x(k + 3), S23, 0xF4D50D87
DO md5_GG WITH b, c, d, a, x(k + 8), S24, 0x455A14ED
DO md5_GG WITH a, b, c, d, x(k + 13), S21, 0xA9E3E905
DO md5_GG WITH d, a, b, c, x(k + 2), S22, 0xFCEFA3F8
DO md5_GG WITH c, d, a, b, x(k + 7), S23, 0x676F02D9
DO md5_GG WITH b, c, d, a, x(k + 12), S24, 0x8D2A4C8A
DO md5_HH WITH a, b, c, d, x(k + 5), S31, 0xFFFA3942
DO md5_HH WITH d, a, b, c, x(k + 8), S32, 0x8771F681
DO md5_HH WITH c, d, a, b, x(k + 11), S33, 0x6D9D6122
DO md5_HH WITH b, c, d, a, x(k + 14), S34, 0xFDE5380C
DO md5_HH WITH a, b, c, d, x(k + 1), S31, 0xA4BEEA44
DO md5_HH WITH d, a, b, c, x(k + 4), S32, 0x4BDECFA9
DO md5_HH WITH c, d, a, b, x(k + 7), S33, 0xF6BB4B60
DO md5_HH WITH b, c, d, a, x(k + 10), S34, 0xBEBFBC70
DO md5_HH WITH a, b, c, d, x(k + 13), S31, 0x289B7EC6
DO md5_HH WITH d, a, b, c, x(k + 0), S32, 0xEAA127FA
DO md5_HH WITH c, d, a, b, x(k + 3), S33, 0xD4EF3085
DO md5_HH WITH b, c, d, a, x(k + 6), S34, 0x4881D05
DO md5_HH WITH a, b, c, d, x(k + 9), S31, 0xD9D4D039
DO md5_HH WITH d, a, b, c, x(k + 12), S32, 0xE6DB99E5
DO md5_HH WITH c, d, a, b, x(k + 15), S33, 0x1FA27CF8
DO md5_HH WITH b, c, d, a, x(k + 2), S34, 0xC4AC5665
DO md5_II WITH a, b, c, d, x(k + 0), S41, 0xF4292244
DO md5_II WITH d, a, b, c, x(k + 7), S42, 0x432AFF97
DO md5_II WITH c, d, a, b, x(k + 14), S43, 0xAB9423A7
DO md5_II WITH b, c, d, a, x(k + 5), S44, 0xFC93A039
DO md5_II WITH a, b, c, d, x(k + 12), S41, 0x655B59C3
DO md5_II WITH d, a, b, c, x(k + 3), S42, 0x8F0CCC92
DO md5_II WITH c, d, a, b, x(k + 10), S43, 0xFFEFF47D
DO md5_II WITH b, c, d, a, x(k + 1), S44, 0x85845DD1
DO md5_II WITH a, b, c, d, x(k + 8), S41, 0x6FA87E4F
DO md5_II WITH d, a, b, c, x(k + 15), S42, 0xFE2CE6E0
DO md5_II WITH c, d, a, b, x(k + 6), S43, 0xA3014314
DO md5_II WITH b, c, d, a, x(k + 13), S44, 0x4E0811A1
DO md5_II WITH a, b, c, d, x(k + 4), S41, 0xF7537E82
DO md5_II WITH d, a, b, c, x(k + 11), S42, 0xBD3AF235
DO md5_II WITH c, d, a, b, x(k + 2), S43, 0x2AD7D2BB
DO md5_II WITH b, c, d, a, x(k + 9), S44, 0xEB86D391
a = AddUnsigned(a, AA)
b = AddUnsigned(b, BB)
c = AddUnsigned(c, CC)
d = AddUnsigned(d, DD)
ENDFOR
ON ERROR &&恢复默认的错误处理
*************下面是输出16位代码的方法*************
* RETURN LOWER(WordToHex(a) + WordToHex(b) + WordToHex(c) + WordToHex(d))
*************下面是输出8位代码的方法*************
RETURN LOWER(WordToHex(b) + WordToHex(c))
ENDFUNC
PROC err_treat
RETURN
ENDPROC
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