Insecure private-key encryption












3












$begingroup$


I am learning about crytography and the differences between the public and private keys encryption examples and I was wondering if it is possible to have a private key encryption scheme that is completely insecure? I have not been able to find what that could look like but I'm curious? Or is this not possible? Is the encryption scheme always secure with private keys?






encryption symmetric







share|improve this question











$endgroup$



migrated from stackoverflow.com 6 hours ago


This question came from our site for professional and enthusiast programmers.























    3












    $begingroup$


    I am learning about crytography and the differences between the public and private keys encryption examples and I was wondering if it is possible to have a private key encryption scheme that is completely insecure? I have not been able to find what that could look like but I'm curious? Or is this not possible? Is the encryption scheme always secure with private keys?






    encryption symmetric







    share|improve this question











    $endgroup$



    migrated from stackoverflow.com 6 hours ago


    This question came from our site for professional and enthusiast programmers.





















      3












      3








      3





      $begingroup$


      I am learning about crytography and the differences between the public and private keys encryption examples and I was wondering if it is possible to have a private key encryption scheme that is completely insecure? I have not been able to find what that could look like but I'm curious? Or is this not possible? Is the encryption scheme always secure with private keys?






      encryption symmetric







      share|improve this question











      $endgroup$




      I am learning about crytography and the differences between the public and private keys encryption examples and I was wondering if it is possible to have a private key encryption scheme that is completely insecure? I have not been able to find what that could look like but I'm curious? Or is this not possible? Is the encryption scheme always secure with private keys?






      encryption symmetric




      encryption symmetric






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited 4 hours ago









      Ilmari Karonen

      35k373138




      35k373138










      asked 11 hours ago







      droidnoob











      migrated from stackoverflow.com 6 hours ago


      This question came from our site for professional and enthusiast programmers.









      migrated from stackoverflow.com 6 hours ago


      This question came from our site for professional and enthusiast programmers.
























          2 Answers
          2






          active

          oldest

          votes


















          5












          $begingroup$

          Any encryption scheme can be insecure if the key space is small enough.



          For example, you could perform encryption with an 8 bit RSA key. For a key of that size, it's trivial to determine the private key given the public key.






          share|improve this answer









          $endgroup$













          • $begingroup$
            would this be true even with a small message space? Or that wouldn't factor in?
            $endgroup$
            – droidnoob
            11 hours ago






          • 1




            $begingroup$
            @droidnoob If your key is insecure nothing else matters. For example given an 8 bit RSA public key with exponent 3 modulus 187, it's trival to factor the modulus into 11 and 17, calculate lamda(187) = lcm(11-1,17-1) = 80, then calculate the private exponent d = 3^-1 mod 80 = 27.
            $endgroup$
            – dbush
            10 hours ago










          • $begingroup$
            thanks for reply. can I ask you one more? What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?
            $endgroup$
            – droidnoob
            10 hours ago






          • 2




            $begingroup$
            @droidnoob If you mean a poorly designed encryption algorithm, then yes.
            $endgroup$
            – dbush
            10 hours ago






          • 2




            $begingroup$
            You could derive a subkey in your scheme that is much smaller than the input key, e.g. by hashing it and taking the leftmost bits. The original, large key could be completely secure - protected by the cryptographic hash - but you have again an encryption scheme with a small key space. Presto.
            $endgroup$
            – Maarten Bodewes♦
            9 hours ago



















          4












          $begingroup$


          What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?




          Yes, certainly. For example, consider the following encryption scheme:




          • The key is a 256 bit (or, heck, 512 or 1024 bit if you want) string chosen uniformly at random by a cryptographically secure true random number generator, stored securely in a locked vault deep underground, with multiple armed guards watching the entrance 24/7.


          • The encryption method doesn't use the key for anything, and instead encrypts the data using rot13.


          • The decryption method is the same as the encryption method.







          share|improve this answer









          $endgroup$













            Your Answer





            StackExchange.ifUsing("editor", function () {
            return StackExchange.using("mathjaxEditing", function () {
            StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
            StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
            });
            });
            }, "mathjax-editing");

            StackExchange.ready(function() {
            var channelOptions = {
            tags: "".split(" "),
            id: "281"
            };
            initTagRenderer("".split(" "), "".split(" "), channelOptions);

            StackExchange.using("externalEditor", function() {
            // Have to fire editor after snippets, if snippets enabled
            if (StackExchange.settings.snippets.snippetsEnabled) {
            StackExchange.using("snippets", function() {
            createEditor();
            });
            }
            else {
            createEditor();
            }
            });

            function createEditor() {
            StackExchange.prepareEditor({
            heartbeatType: 'answer',
            autoActivateHeartbeat: false,
            convertImagesToLinks: false,
            noModals: true,
            showLowRepImageUploadWarning: true,
            reputationToPostImages: null,
            bindNavPrevention: true,
            postfix: "",
            imageUploader: {
            brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
            contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
            allowUrls: true
            },
            noCode: true, onDemand: true,
            discardSelector: ".discard-answer"
            ,immediatelyShowMarkdownHelp:true
            });


            }
            });














            draft saved

            draft discarded


















            StackExchange.ready(
            function () {
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fcrypto.stackexchange.com%2fquestions%2f67586%2finsecure-private-key-encryption%23new-answer', 'question_page');
            }
            );

            Post as a guest















            Required, but never shown
























            2 Answers
            2






            active

            oldest

            votes








            2 Answers
            2






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            5












            $begingroup$

            Any encryption scheme can be insecure if the key space is small enough.



            For example, you could perform encryption with an 8 bit RSA key. For a key of that size, it's trivial to determine the private key given the public key.






            share|improve this answer









            $endgroup$













            • $begingroup$
              would this be true even with a small message space? Or that wouldn't factor in?
              $endgroup$
              – droidnoob
              11 hours ago






            • 1




              $begingroup$
              @droidnoob If your key is insecure nothing else matters. For example given an 8 bit RSA public key with exponent 3 modulus 187, it's trival to factor the modulus into 11 and 17, calculate lamda(187) = lcm(11-1,17-1) = 80, then calculate the private exponent d = 3^-1 mod 80 = 27.
              $endgroup$
              – dbush
              10 hours ago










            • $begingroup$
              thanks for reply. can I ask you one more? What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?
              $endgroup$
              – droidnoob
              10 hours ago






            • 2




              $begingroup$
              @droidnoob If you mean a poorly designed encryption algorithm, then yes.
              $endgroup$
              – dbush
              10 hours ago






            • 2




              $begingroup$
              You could derive a subkey in your scheme that is much smaller than the input key, e.g. by hashing it and taking the leftmost bits. The original, large key could be completely secure - protected by the cryptographic hash - but you have again an encryption scheme with a small key space. Presto.
              $endgroup$
              – Maarten Bodewes♦
              9 hours ago
















            5












            $begingroup$

            Any encryption scheme can be insecure if the key space is small enough.



            For example, you could perform encryption with an 8 bit RSA key. For a key of that size, it's trivial to determine the private key given the public key.






            share|improve this answer









            $endgroup$













            • $begingroup$
              would this be true even with a small message space? Or that wouldn't factor in?
              $endgroup$
              – droidnoob
              11 hours ago






            • 1




              $begingroup$
              @droidnoob If your key is insecure nothing else matters. For example given an 8 bit RSA public key with exponent 3 modulus 187, it's trival to factor the modulus into 11 and 17, calculate lamda(187) = lcm(11-1,17-1) = 80, then calculate the private exponent d = 3^-1 mod 80 = 27.
              $endgroup$
              – dbush
              10 hours ago










            • $begingroup$
              thanks for reply. can I ask you one more? What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?
              $endgroup$
              – droidnoob
              10 hours ago






            • 2




              $begingroup$
              @droidnoob If you mean a poorly designed encryption algorithm, then yes.
              $endgroup$
              – dbush
              10 hours ago






            • 2




              $begingroup$
              You could derive a subkey in your scheme that is much smaller than the input key, e.g. by hashing it and taking the leftmost bits. The original, large key could be completely secure - protected by the cryptographic hash - but you have again an encryption scheme with a small key space. Presto.
              $endgroup$
              – Maarten Bodewes♦
              9 hours ago














            5












            5








            5





            $begingroup$

            Any encryption scheme can be insecure if the key space is small enough.



            For example, you could perform encryption with an 8 bit RSA key. For a key of that size, it's trivial to determine the private key given the public key.






            share|improve this answer









            $endgroup$



            Any encryption scheme can be insecure if the key space is small enough.



            For example, you could perform encryption with an 8 bit RSA key. For a key of that size, it's trivial to determine the private key given the public key.







            share|improve this answer












            share|improve this answer



            share|improve this answer










            answered 11 hours ago









            dbushdbush

            21615




            21615












            • $begingroup$
              would this be true even with a small message space? Or that wouldn't factor in?
              $endgroup$
              – droidnoob
              11 hours ago






            • 1




              $begingroup$
              @droidnoob If your key is insecure nothing else matters. For example given an 8 bit RSA public key with exponent 3 modulus 187, it's trival to factor the modulus into 11 and 17, calculate lamda(187) = lcm(11-1,17-1) = 80, then calculate the private exponent d = 3^-1 mod 80 = 27.
              $endgroup$
              – dbush
              10 hours ago










            • $begingroup$
              thanks for reply. can I ask you one more? What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?
              $endgroup$
              – droidnoob
              10 hours ago






            • 2




              $begingroup$
              @droidnoob If you mean a poorly designed encryption algorithm, then yes.
              $endgroup$
              – dbush
              10 hours ago






            • 2




              $begingroup$
              You could derive a subkey in your scheme that is much smaller than the input key, e.g. by hashing it and taking the leftmost bits. The original, large key could be completely secure - protected by the cryptographic hash - but you have again an encryption scheme with a small key space. Presto.
              $endgroup$
              – Maarten Bodewes♦
              9 hours ago


















            • $begingroup$
              would this be true even with a small message space? Or that wouldn't factor in?
              $endgroup$
              – droidnoob
              11 hours ago






            • 1




              $begingroup$
              @droidnoob If your key is insecure nothing else matters. For example given an 8 bit RSA public key with exponent 3 modulus 187, it's trival to factor the modulus into 11 and 17, calculate lamda(187) = lcm(11-1,17-1) = 80, then calculate the private exponent d = 3^-1 mod 80 = 27.
              $endgroup$
              – dbush
              10 hours ago










            • $begingroup$
              thanks for reply. can I ask you one more? What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?
              $endgroup$
              – droidnoob
              10 hours ago






            • 2




              $begingroup$
              @droidnoob If you mean a poorly designed encryption algorithm, then yes.
              $endgroup$
              – dbush
              10 hours ago






            • 2




              $begingroup$
              You could derive a subkey in your scheme that is much smaller than the input key, e.g. by hashing it and taking the leftmost bits. The original, large key could be completely secure - protected by the cryptographic hash - but you have again an encryption scheme with a small key space. Presto.
              $endgroup$
              – Maarten Bodewes♦
              9 hours ago
















            $begingroup$
            would this be true even with a small message space? Or that wouldn't factor in?
            $endgroup$
            – droidnoob
            11 hours ago




            $begingroup$
            would this be true even with a small message space? Or that wouldn't factor in?
            $endgroup$
            – droidnoob
            11 hours ago




            1




            1




            $begingroup$
            @droidnoob If your key is insecure nothing else matters. For example given an 8 bit RSA public key with exponent 3 modulus 187, it's trival to factor the modulus into 11 and 17, calculate lamda(187) = lcm(11-1,17-1) = 80, then calculate the private exponent d = 3^-1 mod 80 = 27.
            $endgroup$
            – dbush
            10 hours ago




            $begingroup$
            @droidnoob If your key is insecure nothing else matters. For example given an 8 bit RSA public key with exponent 3 modulus 187, it's trival to factor the modulus into 11 and 17, calculate lamda(187) = lcm(11-1,17-1) = 80, then calculate the private exponent d = 3^-1 mod 80 = 27.
            $endgroup$
            – dbush
            10 hours ago












            $begingroup$
            thanks for reply. can I ask you one more? What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?
            $endgroup$
            – droidnoob
            10 hours ago




            $begingroup$
            thanks for reply. can I ask you one more? What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?
            $endgroup$
            – droidnoob
            10 hours ago




            2




            2




            $begingroup$
            @droidnoob If you mean a poorly designed encryption algorithm, then yes.
            $endgroup$
            – dbush
            10 hours ago




            $begingroup$
            @droidnoob If you mean a poorly designed encryption algorithm, then yes.
            $endgroup$
            – dbush
            10 hours ago




            2




            2




            $begingroup$
            You could derive a subkey in your scheme that is much smaller than the input key, e.g. by hashing it and taking the leftmost bits. The original, large key could be completely secure - protected by the cryptographic hash - but you have again an encryption scheme with a small key space. Presto.
            $endgroup$
            – Maarten Bodewes♦
            9 hours ago




            $begingroup$
            You could derive a subkey in your scheme that is much smaller than the input key, e.g. by hashing it and taking the leftmost bits. The original, large key could be completely secure - protected by the cryptographic hash - but you have again an encryption scheme with a small key space. Presto.
            $endgroup$
            – Maarten Bodewes♦
            9 hours ago











            4












            $begingroup$


            What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?




            Yes, certainly. For example, consider the following encryption scheme:




            • The key is a 256 bit (or, heck, 512 or 1024 bit if you want) string chosen uniformly at random by a cryptographically secure true random number generator, stored securely in a locked vault deep underground, with multiple armed guards watching the entrance 24/7.


            • The encryption method doesn't use the key for anything, and instead encrypts the data using rot13.


            • The decryption method is the same as the encryption method.







            share|improve this answer









            $endgroup$


















              4












              $begingroup$


              What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?




              Yes, certainly. For example, consider the following encryption scheme:




              • The key is a 256 bit (or, heck, 512 or 1024 bit if you want) string chosen uniformly at random by a cryptographically secure true random number generator, stored securely in a locked vault deep underground, with multiple armed guards watching the entrance 24/7.


              • The encryption method doesn't use the key for anything, and instead encrypts the data using rot13.


              • The decryption method is the same as the encryption method.







              share|improve this answer









              $endgroup$
















                4












                4








                4





                $begingroup$


                What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?




                Yes, certainly. For example, consider the following encryption scheme:




                • The key is a 256 bit (or, heck, 512 or 1024 bit if you want) string chosen uniformly at random by a cryptographically secure true random number generator, stored securely in a locked vault deep underground, with multiple armed guards watching the entrance 24/7.


                • The encryption method doesn't use the key for anything, and instead encrypts the data using rot13.


                • The decryption method is the same as the encryption method.







                share|improve this answer









                $endgroup$




                What if the key is completely secure and protected, would there be any way to have a completely secure key but insecure scheme?




                Yes, certainly. For example, consider the following encryption scheme:




                • The key is a 256 bit (or, heck, 512 or 1024 bit if you want) string chosen uniformly at random by a cryptographically secure true random number generator, stored securely in a locked vault deep underground, with multiple armed guards watching the entrance 24/7.


                • The encryption method doesn't use the key for anything, and instead encrypts the data using rot13.


                • The decryption method is the same as the encryption method.








                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered 3 hours ago









                Ilmari KaronenIlmari Karonen

                35k373138




                35k373138






























                    draft saved

                    draft discarded




















































                    Thanks for contributing an answer to Cryptography Stack Exchange!


                    • Please be sure to answer the question. Provide details and share your research!

                    But avoid …



                    • Asking for help, clarification, or responding to other answers.

                    • Making statements based on opinion; back them up with references or personal experience.


                    Use MathJax to format equations. MathJax reference.


                    To learn more, see our tips on writing great answers.




                    draft saved


                    draft discarded














                    StackExchange.ready(
                    function () {
                    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fcrypto.stackexchange.com%2fquestions%2f67586%2finsecure-private-key-encryption%23new-answer', 'question_page');
                    }
                    );

                    Post as a guest















                    Required, but never shown





















































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown

































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown







                    -

                    Popular posts from this blog

                    How to label and detect the document text images

                    Image
                    1 $begingroup$ This is what I mean as document text image: I want to label the texts in image as separate blocks and my model should detect these labels as classes. NOTE: This is how the end result should be like: The labels like Block 1, Block 2, Block 3,.. should be Logo, Title, Date,.. Others, etc. Work done: First approach : I tried to implement this method via Object Detection, it didn't work. It didn't even detect any text. Second approach : Then I tried it using PixelLink. As this model is build for scene text detection, it detected each and every text in the image. But this method can detect multiple lines of text if the threshold values are increased. But I have no idea how do I add labels to the text blocks. PIXEL_CLS_WEIGHT_all_ones = 'PIXEL_CLS_WEIGHT_all_ones' PIXEL_C...
                    Read more

                    Vallis Paradisi

                    Image
                    Coordinata: .mw-parser-output .geo-default,.mw-parser-output .geo-dms,.mw-parser-output .geo-dec{display:inline}.mw-parser-output .geo-nondefault,.mw-parser-output .geo-multi-punct{display:none}.mw-parser-output .longitude,.mw-parser-output .latitude{white-space:nowrap} 33°03′S 71°37′W  /  33.05°S 71.617°W  / -33.05; -71.617 Vallis Paradisi Res apud Vicidata repertae: Civitas : Chilia Numerus incolarum : 296 655 Zona horaria : UTC-4 Situs interretialis Nomen officiale : Valparaíso Gubernium Consilium : municipal council of Valparaíso Geographia Superficies : 401 600 000 Metrum quadratum Coniunctiones urbium Urbes gemellae : Ovetum , Badalona , Santa Fe , Ora longa , Sciamhaevum , Quantunia , Callao , Bat Yam , Melaka , Novorossiysk , Busan , Corduba , Odessa , Rosario , Malacca , Barcino , Soteropolis , Franciscopolis (California) , Guanajuato, Silao Tabula aut despectus Despectus in portum sinumque et urbem Vallis Paradisi Vallis Para...
                    Read more

                    Tabula Rosettana

                    Image
                    Tabula multilinguis Rosettana in Museo Britannico ostenditur. Tabula Rosettana, [1] etiam titulo OGIS 90 agnita, est stela decreto de rebus sacris in Aegypto anno 196 a.C.n. lato inscripta. Tabula iuxta Rosettam Aegypti, urbem in delta Nili et ad oram maris Mediterranei iacentem, anno 1799 a milite Francico reperta est. Inventio stelae, linguis duabus scripturisque tribus inscriptae, eruditis Instituti Aegypti statim nuntiata est; ibi enim iussu imperatoris Napoleonis eruditi omnium scientiarum (sub aegide Commissionis Scientiarum et Artium) properaverant cum expeditione Francica. Qua a Britannis mox debellata, tabula Rosettana Londinium missa hodie apud Museum Britannicum iacet. Textus Graecus cito lectus interpretationi textuum Aegyptiorum (in formis hieroglyphica et demotica expressorum) gradatim adiuvit. Denique textum plene interpretatus est Ioannes Franciscus Champollion. Ab opere eruditorum cumulativo coepit hodiernus scripturae hieroglyphicae linguaeque Aegyptiae a...
                    Read more