ASP Base64 encryption and decryption program

<% const BASE_64_MAP_INIT = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" dim nldim Base64EncMap(63) dim Base64DecMap(127) ' must be called before using anything else PUBLIC SUB initCodecs() ' init vars nl = "<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 \ 16) 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 15) ) 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 15)) 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 %>

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