public-key-encryption

Can we have multiple public keys with a single private key for RSA?

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In practice and with respect to security, no, mathematically, yes. If you have a private key (N, D), there is algebraically an infinite number of solutions to the equation 1 = E*D (mod Phi(N)). However, if you make two such solutions (E, N) and (E’, N) that both satisfy the equation public, you will have … Read more

How does the man in the middle attack work in Diffie–Hellman?

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I think you’re confusing the basic Diffie-Hellman, which is a key exchange protocol, with the ‘authenticated version’ which uses a certificate authority (CA). Nice explanation of how the basic Diffie-Hellman is vulnerable to man-in-the-middle from RSA Labs. “The Diffie-Hellman key exchange is vulnerable to a man-in-the-middle attack. In this attack, an opponent Carol intercepts Alice’s … Read more

DH vs. DHE and ECDHE and perfect forward secrecy

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It’s the ephemeral aspect of DHE and ECDHE that provides perfect forward secrecy. The idea is that even if someone records traffic and compromises the server to get its private key, they won’t be able to decipher that traffic, because they’ll be missing the ephemeral DH parameters that won’t have been saved. With fixed DH, … Read more

How to do PGP in Python (generate keys, encrypt/decrypt)

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You don’t need PyCrypto or PyMe, fine though those packages may be – you will have all kinds of problems building under Windows. Instead, why not avoid the rabbit-holes and do what I did? Use gnupg 1.4.9. You don’t need to do a full installation on end-user machines – just gpg.exe and iconv.dll from the … Read more

How to use public and private key encryption technique in C#

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Code example: private static string _privateKey; private static string _publicKey; private static UnicodeEncoding _encoder = new UnicodeEncoding(); private static void RSA() { var rsa = new RSACryptoServiceProvider(); _privateKey = rsa.ToXmlString(true); _publicKey = rsa.ToXmlString(false); var text = “Test1”; Console.WriteLine(“RSA // Text to encrypt: ” + text); var enc = Encrypt(text); Console.WriteLine(“RSA // Encrypted Text: ” + … Read more

RSA Encryption Decryption in Android

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In RSA you should use the public key for encryption and the private key for decryption. Your sample code uses for encryption and decryption the public key – this can not work. Hence in the decryption part you should initialize the cipher this way: cipher1.init(Cipher.DECRYPT_MODE, privateKey); Furthermor your code has a second significant bug: You … Read more