求可逆加密函数，谢谢
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如何用asp进行base64加密?
日期：2001-1-12 17:08:00
出处：china asp
作者：bigeagle
1
2
3OPTION EXPLICIT
4
5const BASE_64_MAP_INIT =
6
7"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
8
9dim nl
10
11' zero based arrays
12
13dim Base64EncMap(63)
14
15dim Base64DecMap(127)
16
17
18
19' must be called before using anything else
20
21PUBLIC SUB initCodecs()
22
23' init vars
24
25nl = "
<p>" & chr(13) & chr(10)
' setup base 64
dim max, idx
max = len(BASE_64_MAP_INIT)
for idx = 0 to max - 1
' one based string
Base64EncMap(idx) = mid(BASE_64_MAP_INIT, idx + 1, 1)
next
for idx = 0 to max - 1
Base64DecMap(ASC(Base64EncMap(idx))) = idx
next
END SUB
' encode base 64 encoded string
PUBLIC FUNCTION base64Encode(plain)
if len(plain) = 0 then
base64Encode = ""
exit function
end if
dim ret, ndx, by3, first, second, third
by3 = (len(plain) \ 3) * 3
ndx = 1
do while ndx <= by3
first = asc(mid(plain, ndx+0, 1))
second = asc(mid(plain, ndx+1, 1))
third = asc(mid(plain, ndx+2, 1))
ret = ret & Base64EncMap( (first \ 4) AND 63 )
ret = ret & Base64EncMap( ((first * 16) AND 48) + ((second \ 16)
AND 15 ) )
ret = ret & Base64EncMap( ((second * 4) AND 60) + ((third \ 64)
AND 3 ) )
ret = ret & Base64EncMap( third AND 63)
ndx = ndx + 3
loop
' check for stragglers
if by3 < len(plain) then
first = asc(mid(plain, ndx+0, 1))
ret = ret & Base64EncMap( (first \ 4) AND 63 )
if (len(plain) MOD 3 ) = 2 then
second = asc(mid(plain, ndx+1, 1))
ret = ret & Base64EncMap( ((first * 16) AND 48) +
((second \
- AND 15 ) )
ret = ret & Base64EncMap( ((second * 4) AND 60) )
else
ret = ret & Base64EncMap( (first * 16) AND 48)
ret = ret & "="
end if
ret = ret & "="
end if
base64Encode = ret
END FUNCTION
' decode base 64 encoded string
PUBLIC FUNCTION base64Decode(scrambled)
if len(scrambled) = 0 then
base64Decode = ""
exit function
end if
' ignore padding
dim realLen
realLen = len(scrambled)
do while mid(scrambled, realLen, 1) = "="
realLen = realLen - 1
loop
dim ret, ndx, by4, first, second, third, fourth
ret = ""
by4 = (realLen \ 4) * 4
ndx = 1
do while ndx <= by4
first = Base64DecMap(asc(mid(scrambled, ndx+0, 1)))
second = Base64DecMap(asc(mid(scrambled, ndx+1, 1)))
third = Base64DecMap(asc(mid(scrambled, ndx+2, 1)))
fourth = Base64DecMap(asc(mid(scrambled, ndx+3, 1)))
ret = ret & chr( ((first * 4) AND 255) + ((second \ 16) AND 3)
)
ret = ret & chr( ((second * 16) AND 255) + ((third \ 4) AND
- )
ret = ret & chr( ((third * 64) AND 255) + (fourth AND 63) )
ndx = ndx + 4
loop
' check for stragglers, will be 2 or 3 characters
if ndx < realLen then
first = Base64DecMap(asc(mid(scrambled, ndx+0, 1)))
second = Base64DecMap(asc(mid(scrambled, ndx+1, 1)))
ret = ret & chr( ((first * 4) AND 255) + ((second \ 16) AND 3)
)
if realLen MOD 4 = 3 then
third = Base64DecMap(asc(mid(scrambled,ndx+2,1)))
ret = ret & chr( ((second * 16) AND 255) + ((third \ 4) AND
- )
end if
end if
base64Decode = ret
END FUNCTION
' initialize
call initCodecs
' Testing code
' dim inp, encode
' inp = request.QueryString("input")
' encode = base64Encode(inp)
' response.write "Encoded value = " & encode & nl
' response.write "Decoded value = " & base64Decode(encode) & nl