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How to prevent roommates from hogging bandwidth
ByEric MaI share a ADSL modem via a Wifi router with several roommates. Sometimes, I find the network bandwidth left is too little. Suspiciously, some one is using BT, Thunder, eMule or other P2P tools. These tools can easily use up all the bandwidth and left little for others. How to prevent some roommates from hogging…
How to not use concrete types in lambda function parameters in C++11?
ByEric MaC++11 requires that lambda function parameters be declared with concrete types. This is sometimes annoying. auto is really nice, especially when the type is complex like std::vector<std::string>::iterator is quite long to type. I know C++14 allows auto in lambda functions. But how to not use concrete types in lambda function parameters in C++11? In C++11,…
Generating RSA Private and Public Key Pair in Go Lang?
How to generate a pair of RSA private and public key in Go lang? Go lang has a rich set of standard libraries. Using Go’s standard libraries, we can generate RSA private and Public keys. The Crypto standard libraries in Go lang Go lang standard libraries has a rich set of cryptography functions. Here are…
How to enable iptables on CentOS 7 / Fedora 20?
ByEric Maiptables is plain old good. How to enable it after I disable firewalld? First, install the iptables-services package as root: # yum install iptables-services Then, start iptables service as root: # touch /etc/sysconfig/iptables # touch /etc/sysconfig/ip6tables # systemctl start iptables # systemctl start ip6tables # systemctl enable iptables # systemctl enable ip6tables Read more: How…
Generating ECDSA K1 and R1 keys using OpenSSL in Linux
ECDSA keys are commonly used in various areas like blockchains. OpenSSL is a commonly used tools in Linux for handling signature/encryption/decryption. This post introduces how to generate ECDSA keys using OpenSSL in Linux. Generate keys for K1 secp256k1 elliptic curve We start with K1 (secp256k1) as the example. To generae ECDSA keys using other curves,…
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How to iterate all dirs and files in a dir in C++?
How to iterate all dirs and files in a dir in C++? To open a dir, we can use opendir() to open a directory stream. DIR *opendir(const char *name); Then we can use readdir() to iterate the directory stream. struct dirent *readdir(DIR *dirp); Here is an example C++ program using these 2 library functions. #include…
