diff --git a/pages/common/openssl.md b/pages/common/openssl.md
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+# openssl
+
+> OpenSSL is a cryptography toolkit.
+
+- Check an SSL connection
+
+`openssl s_client -connect {{domain}}:{{port}}`
+
+- Generate new private key and CSR
+
+`openssl req -out {{path/to/CSR.csr}} -new -newkey rsa:2048 -nodes -keyout {{path/to/pivate.key}}`
+
+- Read contents of a certificate
+
+`openssl x509 -text -noout -in {{path/to/certificate.crt}}`
+
+- Read contents of a private key
+
+`openssl rsa -check -in {{path/to/pivate.key}}`
+
+- Verify a CSR file
+
+`openssl req -text -noout -verify -in {{path/to/CSR.csr}}`
+
+- Check MD5 hash of a certificate
+
+`openssl x509 -noout -modulus -in {{path/to/certificate.crt}} | openssl md5`
+
+- Check MD5 hash of a private key
+
+`openssl rsa -noout -modulus -in {{path/to/pivate.key}} | openssl md5`
+
+- Check MD5 hash of a CSR file
+
+`openssl req -noout -modulus -in {{path/to/CSR.csr}} | openssl md5`