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+# openssl
+
+> OpenSSL is a cryptography toolkit.
+
+- Check an SSL connection
+
+`openssl s_client -connect www.paypal.com:443`
+
+- Generate new private key and CSR
+
+`openssl req -out CSR.csr -new -newkey rsa:2048 -nodes -keyout privateKey.key`
+
+- Read contents of certificate, private key and CSR file
+
+`openssl x509 -text -noout -in certificate.crt`
+`openssl rsa -check -in privateKey.key`
+`openssl req -text -noout -verify -in CSR.csr`
+
+- Check if certificate, private key and CSR have the same MD5 hash
+
+`openssl x509 -noout -modulus -in certificate.crt | openssl md5`
+`openssl rsa -noout -modulus -in privateKey.key | openssl md5`
+`openssl req -noout -modulus -in CSR.csr | openssl md5`