diffie-hellman | 易学教程

Diffie-Hellman密钥交换算法

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简述何为DH密钥间换协议？ DH密钥交换是1976年由Diffie和Hellman共同发明的一种算法。使用这种算法，通信双方仅通过交换一些可以公开的信息就能够生成出共享的密码数字，而这一密码数字就可以被用作对称密码的密钥。IPsec中就使用了经过改良的DH密钥交换。虽然这种方法的名字叫“密钥交换”，但实际上双方并没有真正交换密钥，而是通过计算生成出一个相同的共享密钥。因此，这种方法也称DH密钥协商。 DH内容 DH协议内容如下：协议使用一个质数p的整数模n乘法群以及其原根g Alice与Bob协定使用 p以及base g Alice选择一个秘密整数a, 计算A = g^a mod p并发送给Bob。 Bob选择一个秘密整数b, 计算B = g^b mod p并发送给Alice。 Alice计算alice_key = B a mod p Bob计算bob_key = A b mod p 这样就实现了密钥的交换，互相可以计算出会话密钥。代码实现 #!/usr/bin/python3.7 # -*- coding: utf-8 -*- # @Time : 2019/12/25 17:01 # @Author : SystemDefenser # @Email : mrwx1116@163.com # @Software: PyCharm from random import

Security review of an authenticated Diffie Hellman variant

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问题 EDIT I'm still hoping for some advice on this, i tried to clarify my intentions... When i came upon device pairing in my mobile communication framework i studied a lot of papers on this topic and and also got some input from previous questions here. But, i didn't find a ready to implement protocol solution - so i invented a derivate and as i'm no crypto geek i'm not sure about the security caveats of the final solution: The main questions are Is SHA256 sufficient as a commit function? Is the

Diffie Hellman key agreement generates different key every time JAVA

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问题 I am experiencing a problem with Diffie Hellman implementation. I am using this code http://www.java2s.com/Tutorial/Java/0490__Security/DiffieHellmanKeyAgreement.htm It is actually an example from one book I am reading. But I can't understand why generateSecret() creates a different key for every KeyAgreement . I have noticed the function creates different keys even if I call it with the same KeyAgreement twice! If someone has something to suggest I will be really glad! Thanks for your time!

Convert python long/int to fixed size byte array

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问题 I'm trying to implement RC4 and DH key exchange in python. Problem is that I have no idea about how to convert the python long/int from the key exchange to the byte array I need for the RC4 implementation. Is there a simple way to convert a long to the required length byte array? Update : forgot to mention that the numbers I'm dealing with are 768 bit unsigned integers. 回答1: I haven't done any benchmarks, but this recipe "works for me". The short version: use '%x' % val , then unhexlify the

How to use diffie Hellman Sessionkey as password for AES Encryption

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问题 I need to create a server and client in c++ which exchange Diffie Hellman public key and encryption with AES_256 so far I am using MSDN sample for DH public key Generatinghttps://docs.microsoft.com/en-us/windows/win32/seccrypto/diffie-hellman-keys and its fine with RC4 in both side (client and server) but after Converting sample to AES_256 I get error 0x80090005(NET_BAD_DATA) on client-side EncryptDecrypt API.strange part is if both client and server runs on the same machine (not the same OS)

How to Encode nodejs ecdh public key as pem

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问题 Unable to sign a file with nodejs crypto I am trying to verify a signed document created like in this thread using the method verify.verify() with the ECDH public key. Therefore, i guess, i have to format the raw public key into valid PEM. How would i do that using the ans1.js and bn.js module? 来源： https://stackoverflow.com/questions/50874329/how-to-encode-nodejs-ecdh-public-key-as-pem

Determine Diffie-Hellman “Parameters” Length for a TLS handshake in Java

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问题 I'd like to make an HTTPS connection to a server and, if I'm using non-ephemeral DH key exchange, I'd like to know what the parameters are for that connection. Actually, I don't really care if it's ephemeral or not. What I'm looking for is the ability to make a connection and then warn if the connection is using "weak" DH parameters. Is that something I can check at connection-time? Or is the set of DH parameters (or, more specifically, the length of those parameters, in bits) defined by the

Generate EC Diffie-Hellman public and private key pair

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问题 I need to generate an EC Diffie Hellman key pair. I am using the secp256r1 named curve, and OpenSSL. This is what I have with me so far: unsigned char *ecdh(size_t *secret_len) { EVP_PKEY_CTX *pctx, *kctx; EVP_PKEY_CTX *ctx; unsigned char *secret; EVP_PKEY *pkey = NULL, *peerkey, *params = NULL; /* NB: assumes pkey, peerkey have been already set up */ /* Create the context for parameter generation */ if(NULL == (pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_EC, NULL))) printf("Error in EC key

I'm using Wincrypt for Diffie-Hellman— can I export the shared secret in plain text?

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问题 OK-- thanks to Mike, I was able to get Wincrypt to generate a Diffie-Hellman keypair. I figured out out to export the public key, and how to import the other party's public key. According to the docs, upon import of the other party's public key, the shared secret has been computed. Great. I now need to get ahold of that shared secret, but I don't think its possible. Simply calling CryptExportKey with a type of PLAINTEXTKEYBLOB fails unless I call CryptSetKeyParam to change the algorithm id

Java Diffie-Hellman key exchange

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问题 I'm trying to execute code to perform the Diffie-Hellman key exchange. I sourced the code from an example online (forget where now). I had to import the bouncycastle.jar, which I assumed worked up until execution. my code: package testproject; import java.math.BigInteger; import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.MessageDigest; import java.security.SecureRandom; import java.security.Security; import javax.crypto.KeyAgreement; import javax.crypto