OpenSSL encryption. P.S. The reason this technique works is because if a devious network sniffer tried to replace the certificate with their own modified version, then the client would be able to tell; and the reason the client can tell the certificate has been tampered with is because the client can verify the certificate by converting it into a hash using the same hash function as the CA used when creating its signature (details of the hashing algorithm are part of the certificate). password): You can also use a key file to encrypt/decrypt: first create a key-file: Now we encrypt lik… Well as you can imagine, there is a very high cost and detailed process involved with becoming an authorised CA. With OpenSSL installed and verified on our system, we can so ahead and use it to encrypt and decrypt individual files. Serious business this CA stuff! Making statements based on opinion; back them up with references or personal experience. So far, I figure I should use theese commands: This work fine, except that I loose the first few line of ${content}, which is annoying for plain text content, and fatal when sending binary file. What is the correct way to say I had to move my bike that went under the car in a crash? So let’s start by creating a secret file: OK, so let’s begin with Bob creating a clearsign signature: Once we run this command we can see the file secret.txt.asc was created: Alice can now verify the file was signed by Bob (as she has Bob’s public key already): The downside to using a clearsign signature is three fold: The first is obviously not great, but is OK if you don’t care about the message being visible and you’re only interested in proofing you signed it. The requested length will be 32 (since 32 bytes = 256 bits). OK, so I was going to go through the process of creating a new CA root and then self-signing the certificate so we can then go ahead and issue certificates from our own personal CA. References:Farid's Blog. In order to encrypt the plaintext into a cipher we need to use a technique that relies on the concept of a “key”. Because of the lack of real-time validation checking, the Online Certificate Status Protocol (OCSP) has superseded CRLs in that it is (as the name would suggest) an online resource which systems can query at run-time to verify the validity of a certificate. Here is the first example, this is the client opening communication with the server: As you can see, all the ingredients are there as we described earlier; the cipher suite being the most important to take note of at this time. The easiest way to encrypt a file using OpenSSL is like so (the password for the file is foobar and is specified at the end of the command; you’ll also see we’re using a -salt with the password to help improve the security): To decrypt this file we can use the -d flag (instead of -e which is for encryption): Alternatively you can make things more complex, but ultimately more secure, by encrypting the file using the public key of the person you want to share the file with (which is how GPG works ‘out-of-the-box’). Note: although quite a tough read at times, I would highly recommend “Bulletproof SSL and TLS” written by Ivan Ristić. It’s also worth being aware that GPG will use your system’s entropy to aid its random number generation, so for a brief moment you’ll see it request that you move your cursor around a bit to help build up the entrophy output. Once you do the command: openssl enc -aes-256-cbc -e -in file1 -out file1_encrypted The principle idea being that you generate two keys: As you can probably already guess, the “public” key is something that is safe to become public (i.e. Why aren't "fuel polishing" systems removing water & ice from fuel in aircraft, like in cruising yachts? Which you can get here https://www.feistyduck.com/books/openssl-cookbook/, Although, if you want a super quick run down…, You can generate a CSR (Certificate Signing Request; which you send to a CA to approve) using. Every time your browser interrogates a site’s certificate, it is checking the certs validity period. This is because we have to implicitly trust them to look after our best interests (and only issue certificates to companies/organisations who have proved their true identity through the CAs own rigorous registration process). We arrive at yet another security problem with encrypting data, and although using something like public-key cryptography helps it doesn’t solve the issue of “authentication”. Special care should be taken when handling the private keys especially in a production environment because the whole scheme relies on the senders private key being kept secret. If you echo out the key, you will notice that your browser chokes. These are organisations who can issue certificates on behalf of the original CA (also known as the “Root CA”). Ultimate solution for safe and high secured encode anyone file in OpenSSL and command-line: If she doesn’t, then you’ll have to send her both the signature and the file. In order to get the AES API to work with the ASCII data that I will be feeding it, I needed to setup: A random number that can be used as an Encryption Key; A random number that can be used as an Initialization Vector; A couple of OpenSSL AES_KEY structures for encrypting and decrypting via the API Sinepel / openssl_encrypt_decrypt.php Forked from joashp/openssl_encrypt_decrypt.php. Additionally the libcrypto can be used to perform these operations from a C application. Remember from earlier we discussed how public-key cryptography works and that with it we can secure the communication channel; but at this point we’re still not sure how that happens without exposing the encryption key (necessary to encrypt our data back and forth across the wire) to any devious people sniffing our network traffic. Instead of using openssl to sign and encrypt, consider using a well-established tool that is actually designed to do so securely. Note: if you’re using the Diffie–Hellman key exchange algorithm you’ll find a great visual explanation of the process which uses the analogy of “mixing colours” to indicate the maths behind the equation (e.g. My friend would then be able to decrypt the encrypted file I send to him with: But if someone sends you an encrypted file using your Keybase public key but is encrypted via a different tool, such as their own local GPG or PGP, then you’d decrypt the file with (for example): If you want to encrypt a file for someone who doesn’t use Keybase (e.g. This CRL is downloaded by your browser/operating system on a regular basis and there in lies the problem with CRLs: they’re not real-time results. But if you do use --encrypt with --sign then Alice can’t just use --verify by itself, she has to use --decrypt. This is a set of communicative steps taken between the client (your web browser) and the server. Although OpenSSH does actually utilise OpenSSL for its cryptographic operations, such as key pair generation. It makes using SSH easier (a trade-off of security for convenience) by allowing you to specify your private key password once. So where OpenSSL is designed to provide a method for securing web based communication; OpenSSH on the other hand provides secure and encrypted tunneling capabilities. If you were to ls the current directory they wont be there. Generating a key pair with GPG is a little bit more involved as you have some prompts you need to step through. - thinkoner/openssl Husband. The easiest way to encrypt a file using OpenSSL is like so (the password for the file is foobar and is specified at the end of the command; you’ll also see we’re using a -salt with the password to help improve the security): echo -n 'someTextIWantToEncrypt' | openssl enc -e -salt -out test.txt -aes-256-cbc -pass pass:foobar Imagine a certificate was issued for the website www.foo.com, but later needed to be revoked (for whatever nefarious reason). The benefit of a signature is to allow you to verify that the file (encrypted or plaintext) was indeed created by the person you think it was. You could read out the contents of the public key (e.g. I would suggest they do this in person to avoid network sniffers getting involved and Alice encrypting the file with the wrong details (this is where PKI helps with “authentication” - we don’t have that process/mechanism here unfortunately). GitHub Gist: instantly share code, notes, and snippets. The most popular choice (at the time of writing) is the RSA algorithm, which uses the server’s public key (provided in the certificate the server sends to the client) to encrypt the key before sending it to the server. It only takes a minute to sign up. (assuming you’ve imported their public key already). To learn more, see our tips on writing great answers. the key) that was used to encrypt the plaintext; allowing them to decrypt your cipher and to retrieve your super secret password. Note: in all these examples I use --local-user to change the GPG profile. Well that would be…. You can then self-sign that certificate (while you wait for the CA to officially create you a cert and sign it) using: Note: create key pair + cert in a one liner Two approaches to do this with OpenSSL: (1) generate a random key to be used with a symmetric cipher to encrypt the message and then encrypt the key with RSA; (2) use the smime operation, which combines RSA and a symmetric cipher to automate approach 1. Why is that? (in there are two sub sections about “OpenSSH”, “SSH Agent” and “OpenSSL”, just skip those until you get to the next “GPG” section and continue all the way from there). the website could be who they say they are - your bank - but we can’t really trust them because the certificate they’ve presented to us wasn’t issued by a CA we know of). This is useful because if you’re doing some online banking, you want to be sure that communication between you and the bank are happening privately/securely without anyone being able to sniff your information over the wire. Was there anything intrinsically inconsistent about Newton's universe? Finally, let’s consider ‘attached signatures’. I’ll leave investigation of these settings as an exercise for the reader). Authenticating people is a difficult problem to solve and this is where PKI (Public-key infrastructure) comes in. While in Outlook 2003, it is Sign then Encrypt. The private key is stored in private.pem file and the public key in the public.pem file. your web browser) and another website is handled securely and is happening with the correct/relevant endpoint. If you’ve got ssh-keygen installed, then chances are you’ll have the agent and other OpenSSH tools as well. But I’d like to add onto that some examples of these messages. Instead of signing it yourself, you use the certificate authority you created earlier: openssl x509 -req -days 365 -in cert.csr -CA ca.crt -CAkey ca.key -set_serial 00 -out cert.crt ctest-System-Product-Name ssl # openssl x509 -req -days 365 -in cert.csr -CA ca.crt -CAkey ca.key -set_serial 00 -out cert.crt Signature ok Is it the, Do you have MIME (entity) headers, terminated by an empty line, in the $contents file? Well, the keys are the mathematical inverse of each other; which means you can encrypt data with either the public or private key, and only the alternating key can be used to decrypt the data. -out filename . Also, generating keys is one thing. Then if you want to decrypt the file you simply run: It’ll ask for the passphrase and then it’ll extract the file to the current directory. rev 2021.1.5.38258, The best answers are voted up and rise to the top, Information Security Stack Exchange works best with JavaScript enabled, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, Learn more about hiring developers or posting ads with us. Maybe there are some nefarious government types intercepting your communication and the public key you received is theirs and not Bob’s. You could open an email (or chat program), attach the file and send it to Bob. You’ll see we’re connecting to Google (which is secured using SSL/TLS) and we also specify the -showcerts flag, which allows the response to display all certificates provided within the chain. For example, a devious network sniffer intercepts your initial insecure communication with a server and removes all the cipher suites leaving only the weakest one. The majority of the time if someone mentions they have SSL enabled, then what they probably really mean is that they’re using the TLS protocol. The above sends a request for just the headers for the specified host, and so the response looks something like the following: The following is another example (a non-working example unfortunately), but this time the service we’re querying is utilising self-signed certificates, and so we’re required to provide the CA as well as our own client certificate for authentication: The last example I want to show you is where we try and verify if a particular cipher is disabled (in this case the insecure RC4 cipher): Mozilla released a blog post recently that stated they’ve discontinued support for this particular cipher. The difference is that you have to generate the private key first and then extract the public key from it: You can also print out some additional details contained inside your pem file by using the -text flag: Note: here is a great and detailed article on how to make the most secure key pair process possible. To get the private key, you’ll use a slightly different flag, but effectively it’s the same thing: If you have multiple keys under the same name then you’ll find that it’ll typically export the key for the first name it finds. When I’m setting up my SSH keys for using GitHub I’ll typically run the following commands: Note: I also use the -K flag with ssh-add as that’s specific to Mac OS X. A cipher suite has a structure that looks something like the following: This might just look like a jumble of acronyms, so let’s break down what this means: In the above example, we use RSA which is interpreted as both the key exchange algorithm AND the authentication mechanism. Most operating systems have ssh-agent available. Note: to find the fingerprint of your SSH key use: In order to secure the communication between the client and the server, PKI uses the stages defined within its protocol to fufil what’s commonly referred to as the “SSL handshake”. OpenSSL provides easy command line utilities to both sign and verify documents. Now at this point it’s worth pointing out that certificates are designed to identify websites rather than people and so PKI is built on the premise that you are communicating with a domain/web server. “signed”) by one of these trusted CAs, then your web browser will display a warning that you probably shouldn’t continue on to the website as it doesn’t appear to be who it says it is (i.e. Initially developed by Netscape in 1994 to support the internet’s e-commerce capabilities, Secure Socket Layer (SSL) has come a long way. Now the actual purpose of this post was twofold: Security can be confusing. -in filename . Can anyone please help me to accomplish this? Why is 2 special? Either way this will allow us to connect our shell securely to these remote services/servers. The attachment aspect is sort of theorectical in that it works by explicitly specifying --encrypt, and so if you didn’t use that flag then this example becomes much like --clearsign but with the small benefit of being compressed. This is considered quite a secure set-up (anything less than 2048 bits is easily crackable in todays digital age): Running this command you’ll be asked to provide a name for the keys and an (optional) password. Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Done is because the root CA is set-up, the private and public key for the validity period passed! I suggest to use 4096 bits for the reader ) encrypting and you read. 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