sBASE_64_CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

sBASE_64_CHARACTERS = strUnicode2Ansi(sBASE_64_CHARACTERS)

Function strUnicodeLen(asContents)

'计算unicode字符串的Ansi编码的长度

asContents1="a"&asContents

len1=len(asContents1)

k=

for i= to len1

asc1=asc(mid(asContents1,i,))

if asc1< then asc1=+asc1

if asc1> then

k=k+

else

k=k+

end if

next

strUnicodeLen=k-

End Function

Function strUnicode2Ansi(asContents)

'将Unicode编码的字符串，转换成Ansi编码的字符串

strUnicode2Ansi=""

len1=len(asContents)

for i= to len1

varchar=mid(asContents,i,)

varasc=asc(varchar)

if varasc< then varasc=varasc+

if varasc> then

varHex=Hex(varasc)

varlow=left(varHex,)

varhigh=right(varHex,)

strUnicode2Ansi=strUnicode2Ansi & chrb("&H" & varlow ) & chrb("&H" & varhigh )

else

strUnicode2Ansi=strUnicode2Ansi & chrb(varasc)

end if

next

End function

Function strAnsi2Unicode(asContents)

'将Ansi编码的字符串，转换成Unicode编码的字符串

strAnsi2Unicode = ""

len1=lenb(asContents)

if len1= then exit function

for i= to len1

varchar=midb(asContents,i,)

varasc=ascb(varchar)

if varasc >  then

strAnsi2Unicode = strAnsi2Unicode & chr(ascw(midb(asContents,i+,) & varchar))

i=i+

else

strAnsi2Unicode = strAnsi2Unicode & chr(varasc)

end if

next

End function

Function Base64encode(asContents)

'将Ansi编码的字符串进行Base64编码

'asContents应当是ANSI编码的字符串（二进制的字符串也可以）

Dim lnPosition

Dim lsResult

Dim Char1

Dim Char2

Dim Char3

Dim Char4

Dim Byte1

Dim Byte2

Dim Byte3

Dim SaveBits1

Dim SaveBits2

Dim lsGroupBinary

Dim lsGroup64

Dim m4,len1,len2

len1=Lenb(asContents)

if len1< then

Base64encode=""

exit Function

end if

m3=Len1 Mod

If M3 >  Then asContents = asContents & String(-M3, chrb())

'补足位数是为了便于计算

IF m3 >  THEN

len1=len1+(-m3)

len2=len1-

else

len2=len1

end if

lsResult = ""

For lnPosition =  To len2 Step

lsGroup64 = ""

lsGroupBinary = Midb(asContents, lnPosition, )

Byte1 = Ascb(Midb(lsGroupBinary, , )): SaveBits1 = Byte1 And

Byte2 = Ascb(Midb(lsGroupBinary, , )): SaveBits2 = Byte2 And

Byte3 = Ascb(Midb(lsGroupBinary, , ))

Char1 = Midb(sBASE_64_CHARACTERS, ((Byte1 And ) / ) + , )

Char2 = Midb(sBASE_64_CHARACTERS, (((Byte2 And ) / ) Or (SaveBits1 * ) And &HFF) + , )

Char3 = Midb(sBASE_64_CHARACTERS, (((Byte3 And ) / ) Or (SaveBits2 * ) And &HFF) + , )

Char4 = Midb(sBASE_64_CHARACTERS, (Byte3 And ) + , )

lsGroup64 = Char1 & Char2 & Char3 & Char4

lsResult = lsResult & lsGroup64

Next

'处理最后剩余的几个字符

if M3 >  then

lsGroup64 = ""

lsGroupBinary = Midb(asContents, len2+, )

Byte1 = Ascb(Midb(lsGroupBinary, , )): SaveBits1 = Byte1 And

Byte2 = Ascb(Midb(lsGroupBinary, , )): SaveBits2 = Byte2 And

Byte3 = Ascb(Midb(lsGroupBinary, , ))

Char1 = Midb(sBASE_64_CHARACTERS, ((Byte1 And ) / ) + , )

Char2 = Midb(sBASE_64_CHARACTERS, (((Byte2 And ) / ) Or (SaveBits1 * ) And &HFF) + , )

Char3 = Midb(sBASE_64_CHARACTERS, (((Byte3 And ) / ) Or (SaveBits2 * ) And &HFF) + , )

if M3= then

lsGroup64 = Char1 & Char2 & ChrB() & ChrB() '用=号补足位数

else

lsGroup64 = Char1 & Char2 & Char3 & ChrB() '用=号补足位数

end if

lsResult = lsResult & lsGroup64

end if

Base64encode = lsResult

End Function

Function Base64decode(asContents)

'将Base64编码字符串转换成Ansi编码的字符串

'asContents应当也是ANSI编码的字符串（二进制的字符串也可以）

Dim lsResult

Dim lnPosition

Dim lsGroup64, lsGroupBinary

Dim Char1, Char2, Char3, Char4

Dim Byte1, Byte2, Byte3

Dim M4,len1,len2

len1= Lenb(asContents)

M4 = len1 Mod 

if len1 <  or M4 >  then

'字符串长度应当是4的倍数

Base64decode = ""

exit Function

end if

'判断最后一位是不是 = 号

'判断倒数第二位是不是 = 号

'这里m4表示最后剩余的需要单独处理的字符个数

if midb(asContents, len1, ) = chrb() then m4=

if midb(asContents, len1-, ) = chrb() then m4=

if m4 =  then

len2=len1

else

len2=len1-

end if

For lnPosition =  To Len2 Step

lsGroupBinary = ""

lsGroup64 = Midb(asContents, lnPosition, )

Char1 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, , )) -

Char2 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, , )) -

Char3 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, , )) -

Char4 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, , )) -

Byte1 = Chrb(((Char2 And ) / ) Or (Char1 * ) And &HFF)

Byte2 = lsGroupBinary & Chrb(((Char3 And ) / ) Or (Char2 * ) And &HFF)

Byte3 = Chrb((((Char3 And ) * ) And &HFF) Or (Char4 And ))

lsGroupBinary = Byte1 & Byte2 & Byte3

lsResult = lsResult & lsGroupBinary

Next

'处理最后剩余的几个字符

if M4 >  then

lsGroupBinary = ""

lsGroup64 = Midb(asContents, len2+, m4) & chrB() 'chr(65)=A，转换成值为0

if M4= then '补足4位，是为了便于计算

lsGroup64 = lsGroup64 & chrB()

end if

Char1 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, , )) -

Char2 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, , )) -

Char3 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, , )) -

Char4 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, , )) -

Byte1 = Chrb(((Char2 And ) / ) Or (Char1 * ) And &HFF)

Byte2 = lsGroupBinary & Chrb(((Char3 And ) / ) Or (Char2 * ) And &HFF)

Byte3 = Chrb((((Char3 And ) * ) And &HFF) Or (Char4 And ))

if M4= then

lsGroupBinary = Byte1

elseif M4= then

lsGroupBinary = Byte1 & Byte2

end if

lsResult = lsResult & lsGroupBinary

end if

Base64decode = lsResult

End Function

'加密

strAnsi2Unicode(Base64encode(strUnicode2Ansi("加密字符串")))

'解密

strAnsi2Unicode(Base64decode(strUnicode2Ansi("解密字符串")))