Creating a Digital Signature
I am developing an application (standalone application) in C that runs on linux platform. I have some problems with some of the actions in this application such as, (i) Creating a digital signature for a message ,(ii) Encrypting the message and
(iii) Decrypting the message. Please help me...
Well, for 2 and 3, it's very simple. Just make some characters eqal another character. Like, if I were to type in 'i', and you wanted to encrypt it, then make it equal to "es". Then, when the message is recieved, then it will get it as "es", and just convert it to 'i'. I hope you understood this.
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-gnu-ehacks
That's the worst encryption method ever(if it can even be called encryption), and the solution to every one of those letter substitution can be found at your local library, in a damn Sherlock Holmes book.Originally posted by gnu-ehacks
Well, for 2 and 3, it's very simple. Just make some characters eqal another character. Like, if I were to type in 'i', and you wanted to encrypt it, then make it equal to "es". Then, when the message is recieved, then it will get it as "es", and just convert it to 'i'. I hope you understood this.
heh, Sunday word jumble, anyone?
For creating a digital signature for a message, try searching for the MD2, MD4 and MD5 algorithms. Probably somewhere on rfc-editor.com...
.sect signature
MD5 0wnz j00
also don't use simple substitution ciphers for reasons that won't fit in this board., Also don't use simple xor encryption.... *shudders*
one fish two fish
red fish blue fish
Hi,
Encryption algorithm MD2, MD4 and MD5.. DES, the address rfc-editor.com not working.
Reference from any other site?
[ Never code before desk work ]
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For encryption/decryption/signatures using public key cryptography, I could refer you to the following site
http://www.openssl.org/docs
I know it might be pretty much like diving into the middle of an ocean, but persevere, here are some guidelines, look for the following functions
RSA_size
RSA_generate_key
RSA_public_encrypt
RSA_private_decrypt
RSA_public_decrypt
RSA_private_encrypt
RSA_sign
The beggining is not that easy, don't expect it to be. As for substitutions, I kind of would not advise it.
Good Luck.
-------------------------
Gerald.
If your program fails to compile and gives messages like:
try compiling like thisCode:tmp/ccMNhYc6.o: In function `main': /tmp/ccMNhYc6.o(.text+0x2d): undefined reference to `RSA_generate_key' /tmp/ccMNhYc6.o(.text+0x5a): undefined reference to `RSA_size' /tmp/ccMNhYc6.o(.text+0x85): undefined reference to `RSA_public_encrypt' /tmp/ccMNhYc6.o(.text+0xd3): undefined reference to `RSA_size' /tmp/ccMNhYc6.o(.text+0xf5): undefined reference to `RSA_size' /tmp/ccMNhYc6.o(.text+0x131): undefined reference to `RSA_private_decrypt'
$ gcc -o <outputname> -lcrypto <programfilename>
if this doesn't work, start searching for the openssl libraries.
-------------------------
Gerald.
