Hi All,
This is just to make clear some of the concepts used for encrypting and decrypting a file.

I use crypto++ lib for reference.

Some of common questions:
1) What is a 'seed' in cryptography?
2) I have a plain text file with size say '20kb'. When I encrypt the file the file size is increased. Why?
3) crypto++ provides alogorithms to encrypt and decrypt the files. To either encrypt and decrypt we need to write some logic which can make use of algorithms.
Consider for example I have this code snippet
Qt Code: 
  1. string EncryptString(const char *instr, const char *passPhrase)
  2. {
  3. 	string outstr;
  4.  
  5. 	DefaultEncryptorWithMAC encryptor(passPhrase, new HexEncoder(new StringSink(outstr)));
  6. 	encryptor.Put((byte *)instr, strlen(instr));
  7. 	encryptor.MessageEnd();
  8.  
  9. 	return outstr;
  10. }
  11.  
  12. string DecryptString(const char *instr, const char *passPhrase)
  13. {
  14. 	string outstr;
  15.  
  16. 	HexDecoder decryptor(new DefaultDecryptorWithMAC(passPhrase, new StringSink(outstr)));
  17. 	decryptor.Put((byte *)instr, strlen(instr));
  18. 	decryptor.MessageEnd();
  19.  
  20. 	return outstr;
  21. }
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Now in the above code there is logic to encrypt and decrpt a string.
1) Suppose there is a hacker who knows the passpharse of string and even know what alogorithm was used to encrypt it ( DefaultEncryptorWithMAC in above case). Is it possible for the hacker to decrypt the string with above information(only passpharse and algorithm used) ?
2) What do I call the logic part written above in technical terms? Suppose I want to explain my peers about how I used the logic to encrypt and decrypt the files. Is this what you call 'seed'?
3) I will encrypt a file with say AES::CBC mode and use passpharse 'hello123'. Now I have a friend in Poland whom I send the file by an attachment. I even reveal my passpharse and algorithm used (AES::CBC) but not the logic I have written to encode. Is it possible for my friend to decrypt the file using crypto++ lib?

The above questions might sound stupid so please bear with me?
Thanks