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<div align="left" ><font face="Arial" size="4" ><span style="font-size:14pt" >Overview</span></font><font color="#010101" ></font></div>
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<hr><div align="left" ><font face="Times New Roman" color="#010101" ><span style="font-size:12pt" >Using the Crypto library you can encrypt and decrypt data with a specified key.</span></font><font color="#010101" ></font></div><div align="left" ><font face="Times New Roman" color="#010101" ><span style="font-size:12pt" >The Crypto library uses the Crypto API methods.</span></font><font color="#010101" ></font></div><div align="left" ><font face="Times New Roman" color="#010101" ><span style="font-size:12pt" >You must supply the same PassPhrase string when you encrypt and decrypt the data.</span></font><font color="#010101" ></font></div><div align="left" ><font face="Times New Roman" color="#010101" ><span style="font-size:12pt" >A 128 bit hash object is created from the PassPhrase (using the MD5 algorithm), and
from that object a 40 bit crypto key is generated.</span></font><font color="#010101" ></font></div><div align="left" ><font face="Times New Roman" color="#010101" ><span style="font-size:12pt" >The PassPhrase string should not be saved inside the code (as string).</span></font><font color="#010101" ></font></div><div align="left" ><br></div><font color="#010101" ><div align="left" ></font><font face="Times New Roman" color="#010101" ><span style="font-size:12pt" >Example: (you can download this example from Basic4ppc site)</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#008000" ><span style="font-size:10pt" >'Crypto is a Crypto object and Bit is a Bitwise object</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >Sub </span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" >Globals</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > </span></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >Dim </span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" >string(0) </span></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >as </span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" >Byte, secret(0) </span></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >as </span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" >Byte </span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" ><span style="font-size:10pt" > PassPhrase = "my key" </span></font><font face="Courier New" color="#008000" ><span style="font-size:10pt" >'This is not recommended in real
applications!!!</span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" > </span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >End Sub</span></font><font color="#010101" ></font></div><div align="left" ><br></div><font color="#010101" ><div align="left" ></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >Sub </span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" >App_Start</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > Form1.Show</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > Bit.New1</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > Crypto.New1</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >End Sub</span></font><font color="#010101" ></font></div><div align="left" ><br></div><font color="#010101" ><div align="left" ></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >Sub </span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" >btnEncrypt_Click</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > string() =
Bit.StringToBytes(txtString.Text,0,</span></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >StrLength</span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" >(txtString.Text)) </span></font><font face="Courier New" color="#008000" ><span style="font-size:10pt" >'Convert
the string to an array of bytes.</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > secret() = Crypto.Encrypt(PassPhrase, string()) </span></font><font face="Courier New" color="#008000" ><span style="font-size:10pt" >'Save the
encrypted data.</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > </span></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >for</span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" > i = 0 </span></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >to</span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" > </span></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >ArrayLen</span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" >(secret())-1 </span></font><font face="Courier New" color="#008000" ><span style="font-size:10pt" >'Show the encrypted data in the
TextBox</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > s = s & bit.DecToHex(secret(i))</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > </span></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >next</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > txtString.Text = s</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >End Sub</span></font><font color="#010101" ></font></div><div align="left" ><br></div><font color="#010101" ><div align="left" ></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >Sub </span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" >btnDecrypt_Click</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > string() = Crypto.Decrypt(PassPhrase,secret()) </span></font><font face="Courier New" color="#008000" ><span style="font-size:10pt" >'Decrypt the data.</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#010101" ><span style="font-size:10pt" > txtString.Text = Bit.BytesToString(string(),0,</span></font><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >ArrayLen</span></font><font face="Courier New" color="#010101" ><span style="font-size:10pt" >(string())) </span></font><font face="Courier New" color="#008000" ><span style="font-size:10pt" >'Convert the array to a string.</span></font><font color="#010101" ></font></div><div align="left" ><font face="Courier New" color="#0000ff" ><span style="font-size:10pt" >End Sub</span></font><font color="#010101" ></font></div>
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