Home    Training    Downloads    Tutorials    Arbitary    Get Fate    Proxy Info
 
Training session 8: Basic Encryption
Difficulty: Medium
Learn how a Base 64 Encryption Works
Creator: m101


As the name suggests, Base 64 Encryptions work by converting strings to Base 64. The first thing we do is take a string we want to encrypt 'Hello' and find the dicimal equivilant for every character in it:

Char  Dec  Oct  Hex | Char  Dec  Oct  Hex | Char  Dec  Oct  Hex | Char Dec  Oct   Hex
-------------------------------------------------------------------------------------
(nul)   0 0000 0x00 | (sp)   32 0040 0x20 | @      64 0100 0x40 | `      96 0140 0x60
(soh)   1 0001 0x01 | !      33 0041 0x21 | A      65 0101 0x41 | a      97 0141 0x61
(stx)   2 0002 0x02 | "      34 0042 0x22 | B      66 0102 0x42 | b      98 0142 0x62
(etx)   3 0003 0x03 | #      35 0043 0x23 | C      67 0103 0x43 | c      99 0143 0x63
(eot)   4 0004 0x04 | $      36 0044 0x24 | D      68 0104 0x44 | d     100 0144 0x64
(enq)   5 0005 0x05 | %      37 0045 0x25 | E      69 0105 0x45 | e     101 0145 0x65
(ack)   6 0006 0x06 | &      38 0046 0x26 | F      70 0106 0x46 | f     102 0146 0x66
(bel)   7 0007 0x07 | '      39 0047 0x27 | G      71 0107 0x47 | g     103 0147 0x67
(bs)    8 0010 0x08 | (      40 0050 0x28 | H      72 0110 0x48 | h     104 0150 0x68
(ht)    9 0011 0x09 | )      41 0051 0x29 | I      73 0111 0x49 | i     105 0151 0x69
(nl)   10 0012 0x0a | *      42 0052 0x2a | J      74 0112 0x4a | j     106 0152 0x6a
(vt)   11 0013 0x0b | +      43 0053 0x2b | K      75 0113 0x4b | k     107 0153 0x6b
(np)   12 0014 0x0c | ,      44 0054 0x2c | L      76 0114 0x4c | l     108 0154 0x6c
(cr)   13 0015 0x0d | -      45 0055 0x2d | M      77 0115 0x4d | m     109 0155 0x6d
(so)   14 0016 0x0e | .      46 0056 0x2e | N      78 0116 0x4e | n     110 0156 0x6e
(si)   15 0017 0x0f | /      47 0057 0x2f | O      79 0117 0x4f | o     111 0157 0x6f
(dle)  16 0020 0x10 | 0      48 0060 0x30 | P      80 0120 0x50 | p     112 0160 0x70
(dc1)  17 0021 0x11 | 1      49 0061 0x31 | Q      81 0121 0x51 | q     113 0161 0x71
(dc2)  18 0022 0x12 | 2      50 0062 0x32 | R      82 0122 0x52 | r     114 0162 0x72
(dc3)  19 0023 0x13 | 3      51 0063 0x33 | S      83 0123 0x53 | s     115 0163 0x73
(dc4)  20 0024 0x14 | 4      52 0064 0x34 | T      84 0124 0x54 | t     116 0164 0x74
(nak)  21 0025 0x15 | 5      53 0065 0x35 | U      85 0125 0x55 | u     117 0165 0x75
(syn)  22 0026 0x16 | 6      54 0066 0x36 | V      86 0126 0x56 | v     118 0166 0x76
(etb)  23 0027 0x17 | 7      55 0067 0x37 | W      87 0127 0x57 | w     119 0167 0x77
(can)  24 0030 0x18 | 8      56 0070 0x38 | X      88 0130 0x58 | x     120 0170 0x78
(em)   25 0031 0x19 | 9      57 0071 0x39 | Y      89 0131 0x59 | y     121 0171 0x79
(sub)  26 0032 0x1a | :      58 0072 0x3a | Z      90 0132 0x5a | z     122 0172 0x7a
(esc)  27 0033 0x1b | ;      59 0073 0x3b | [      91 0133 0x5b | {     123 0173 0x7b
(fs)   28 0034 0x1c | <      60 0074 0x3c | \      92 0134 0x5c | |     124 0174 0x7c
(gs)   29 0035 0x1d | =      61 0075 0x3d | ]      93 0135 0x5d | }     125 0175 0x7d
(rs)   30 0036 0x1e | >      62 0076 0x3e | ^      94 0136 0x5e | ~     126 0176 0x7e
(us)   31 0037 0x1f | ?      63 0077 0x3f | _      95 0137 0x5f | (del) 127 0177 0x7f


Now after reading off the decimal value of each character you should have the following:

H= 72
e= 101
l= 108
l= 108
o= 111

Convert each value to binary, if you dont know how to do this please read the earlier tutorials. Once you have converted the values you should get:

72= 01001000
101= 01100101
108= 01101100
108= 01101100
111= 01101111

So this tells us that 'Hello' can be written in Binary as '01001000 01100101 01101100 01101100 01101111'

Each Binary group consists of eight characters, since '11111111' = 255 but including 0 has 256 characters, we call this base 256. Take off a digit and it becomes Base 128 and remove yet another digit and you are left with '111111' which is base 64. So now you know that to convert a number to Base 64 all you have to do is 'shift' the position of the characters and the base will change. Back to the encryption, take the string and join it so you get:

0100100001100101011011000110110001101111

Take this number and divide it into groups of six and you should get:

010010 000110 010101 101100 011011 000110 001111

Dont forget to add the digits to the last number to make it a group of six. Simply conver each number back into decimal and you have the Decimal value of the Encrypted string.

18 6 21 44 27 6 15

Add 33 to each value, as 33 is the value of 'A' in decimal which is the lowest common keyboard character and you will get:

51 39 54 77 60 39 48

Which in ASCII is:

SGVsbG8

But since Base 64 Encryption works in blocks of four, you have to add a '=' to the end and you are left with:

SGVsbG8=

You have just encrypted a string with a Base 64 Encryption!

Now you ask, i can encrypt the function, i can easily decypt it by reversing the proccess, but what is the point of it? Well Base 64 Encryption can be used to quickly encrypt small messages, but is more commonly used in HTTP authorisation requests to encrypt usernames and passwords. A HTTP username and password is make by taking the username, adding a single ':' in the centre and then putting a password on the end so a username of 'l33t' and a password of 'c0der' would look like:

l33t:c0der

Now that string is encrypted and you are left with:

bDMzdDpjMGRlcg==

Although there is many programs available to encrypt this, below is a function that can easily be added to a Visual Basic Project to encrypt strings for you. To use it just place it into the main code and call Base64_Encode("String_to_Encode") and it will return the encrypted string.

Private Function Base64_Encode(strSource) As String
    '
    Const BASE64_TABLE As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    '
    Dim strTempLine As String
    Dim j As Integer
    '
    For j = 1 To (Len(strSource) - Len(strSource) Mod 3) Step 3
        'Breake each 3 (8-bits) bytes to 4 (6-bits) bytes
        '
        '1 byte
        strTempLine = strTempLine + Mid(BASE64_TABLE, (Asc(Mid(strSource, j, 1)) \ 4) + 1, 1)
        '2 byte
        strTempLine = strTempLine + Mid(BASE64_TABLE, ((Asc(Mid(strSource, j, 1)) Mod 4) * 16 _
                       + Asc(Mid(strSource, j + 1, 1)) \ 16) + 1, 1)
        '3 byte
        strTempLine = strTempLine + Mid(BASE64_TABLE, ((Asc(Mid(strSource, j + 1, 1)) Mod 16) * 4 _
                       + Asc(Mid(strSource, j + 2, 1)) \ 64) + 1, 1)
        '4 byte
        strTempLine = strTempLine + Mid(BASE64_TABLE, (Asc(Mid(strSource, j + 2, 1)) Mod 64) + 1, 1)
    Next j
    '
    If Not (Len(strSource) Mod 3) = 0 Then
        '
        If (Len(strSource) Mod 3) = 2 Then
            '
            strTempLine = strTempLine + Mid(BASE64_TABLE, (Asc(Mid(strSource, j, 1)) \ 4) + 1, 1)
            '
            strTempLine = strTempLine + Mid(BASE64_TABLE, (Asc(Mid(strSource, j, 1)) Mod 4) * 16 _
                       + Asc(Mid(strSource, j + 1, 1)) \ 16 + 1, 1)
            '
            strTempLine = strTempLine + Mid(BASE64_TABLE, (Asc(Mid(strSource, j + 1, 1)) Mod 16) * 4 + 1, 1)
            '
            strTempLine = strTempLine & "="
            '
        ElseIf (Len(strSource) Mod 3) = 1 Then
            '
            '
            strTempLine = strTempLine + Mid(BASE64_TABLE, Asc(Mid(strSource, j, 1)) \ 4 + 1, 1)
            '
            strTempLine = strTempLine + Mid(BASE64_TABLE, (Asc(Mid(strSource, j, 1)) Mod 4) * 16 + 1, 1)
            '
            strTempLine = strTempLine & "=="
            '
        End If
        '
    End If
    '
    Base64_Encode = strTempLine
    '
End Function
Name

URL or Email

Message