يتطلب كل تطبيق برمجي اسم مستخدم وكلمة مرور من أجل مصادقة المستخدم الصالح. يمكن أن يكون اسم المستخدم بمثابة معرف بريد إلكتروني أو مجرد مجموعة من الأحرف. ولكن أثناء إنشاء كلمة المرور، يجب على المرء أن يكون حذرا للغاية. لأن أي شخص لديه بيانات اعتماد صالحة يمكنه الدخول إلى النظام والوصول إلى المعلومات.

الحاجة إلى تشفير كلمة المرور

عندما يقوم المستخدم بتعيين كلمة المرور الخاصة به، يتم تخزينها في قاعدة البيانات كنص عادي. إن تخزين النص العادي كما هو في قاعدة البيانات ليس آمنًا على الإطلاق. يمكن للمتسللين كسر النظام وسرقة كلمات المرور من قاعدة البيانات.

لضمان أمان كلمة المرور الخاصة بالمستخدم، يتم تشفيرها باستخدام تقنيات تشفير مختلفة. باستخدام تقنيات التشفير المختلفة، يتم تخزين كلمة المرور ذات النص العادي في نموذج مشفر في قاعدة البيانات. هناك العديد من الطرق التي يمكن استخدامها لتشفير كلمة المرور. لكن التجزئة هي إحدى تقنيات التشفير الأكثر شيوعًا.

تقنيات التجزئة الآمنة لجافا

يتم إنشاء قيمة التجزئة المشفرة باستخدام خوارزميات معينة على كلمة مرور النص العادي المقدمة من قبل المستخدم. تدعم برمجة Java العديد من تقنيات التجزئة لتشفير كلمة المرور.

تقنية التجزئة MD5

تعد MD5 (Message Digest) خوارزمية تجزئة شائعة جدًا. إنها وظيفة تجزئة تشفير تولد قيمة تجزئة 128 بت. يتم تعريف هذه الخوارزمية ضمن حزمة java.security في برمجة Java.

PassEncTech1.java

 import java.security.NoSuchAlgorithmException; import java.security.MessageDigest; public class PassEncTech1 { /* Driver Code */ public static void main(String[] args) { /* Plain-text password initialization. */ String password = &apos;myPassword&apos;; String encryptedpassword = null; try { /* MessageDigest instance for MD5. */ MessageDigest m = MessageDigest.getInstance(&apos;MD5&apos;); /* Add plain-text password bytes to digest using MD5 update() method. */ m.update(password.getBytes()); /* Convert the hash value into bytes */ byte[] bytes = m.digest(); /* The bytes array has bytes in decimal form. Converting it into hexadecimal format. */ StringBuilder s = new StringBuilder(); for(int i=0; i <bytes.length ;i++) { s.append(integer.tostring((bytes[i] & 0xff) + 0x100, 16).substring(1)); } * complete hashed password in hexadecimal format encryptedpassword="s.toString();" catch (nosuchalgorithmexception e) e.printstacktrace(); display the unencrypted and encrypted passwords. system.out.println('plain-text password: ' password); system.out.println('encrypted using md5: encryptedpassword); < pre> <p> <strong>Output:</strong> </p> <pre> Plain-text password: myPassword Encrypted password using MD5: deb1536f480475f7d593219aa1afd74c </pre> <p>The above code shows the implementation of <strong> <em>MessageDigest</em> </strong> class in <strong> <em>java.security</em> </strong> package. The MD5 returns a byte array that needs to be converted into a readable hexadecimal format.</p> <p>The MD5 hashing technique is easy and fast to implement but it is also prone to brute force attacks or dictionary attacks.</p> <h3>SHA256</h3> <p>SHA is the Secure Hash Algorithm. It uses a cryptographic function that takes up the 32-bit plain-text password and converts it into a fixed size 256-bit hash value. This hashing technique is implemented using the MessageDiagest class of java.security package.</p> <p>It is a one-way encryption technique. Once the passphrase is encrypted it cannot be decrypted back.</p> <p> <strong>PassEncTech2.java</strong> </p> <pre> import java.math.BigInteger; import java.nio.charset.StandardCharsets; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; public class PassEncTech2 { public static byte[] getSHA(String input) throws NoSuchAlgorithmException { /* MessageDigest instance for hashing using SHA256 */ MessageDigest md = MessageDigest.getInstance(&apos;SHA-256&apos;); /* digest() method called to calculate message digest of an input and return array of byte */ return md.digest(input.getBytes(StandardCharsets.UTF_8)); } public static String toHexString(byte[] hash) { /* Convert byte array of hash into digest */ BigInteger number = new BigInteger(1, hash); /* Convert the digest into hex value */ StringBuilder hexString = new StringBuilder(number.toString(16)); /* Pad with leading zeros */ while (hexString.length() <32) { hexstring.insert(0, '0'); } return hexstring.tostring(); * driver code public static void main(string args[]) try string string1="myPassword" ; system.out.println('
' + ' : tohexstring(getsha(string1))); string2="hashtrial" tohexstring(getsha(string2))); catch (nosuchalgorithmexception e) system.out.println('exception thrown for incorrect algorithm: e); < pre> <p> <strong>Output:</strong> </p> <pre> myPassword : 76549b827ec46e705fd03831813fa52172338f0dfcbd711ed44b81a96dac51c6 hashtrial : d3e3224a59d69e9a000f1ce6782cb6a8be1eb3155610ff41bffbcbc95adc5d7 </pre> <p>The above code uses the instance of <strong> <em>MessageDigest</em> </strong> class to generate a hash for <strong> <em>SHA256</em> </strong> . The SHA256 returns a byte array that needs to be converted into a readable hexadecimal format. And lastly, the encrypted hash value is displayed.</p> <h3>SHA512 MD5 Hashing Technique</h3> <p>SHA512 uses a cryptographic function that takes up the 64-bit plain-text password and converts it into a fixed size 512-bit hash value. This hashing technique is also implemented using the MessageDiagest class of java.security package.</p> <p> <strong>PassEncTech2.java</strong> </p> <pre> import java.math.BigInteger; import java.nio.charset.StandardCharsets; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; public class PassEncTech2 { public static byte[] getSHA(String input) throws NoSuchAlgorithmException { /* MessageDigest instance for hashing using SHA512*/ MessageDigest md = MessageDigest.getInstance(&apos;SHA-512&apos;); /* digest() method called to calculate message digest of an input and return array of byte */ return md.digest(input.getBytes(StandardCharsets.UTF_8)); } public static String toHexString(byte[] hash) { /* Convert byte array of hash into digest */ BigInteger number = new BigInteger(1, hash); /* Convert the digest into hex value */ StringBuilder hexString = new StringBuilder(number.toString(16)); /* Pad with leading zeros */ while (hexString.length() <32) { hexstring.insert(0, '0'); } return hexstring.tostring(); * driver code public static void main(string args[]) try string string1="myPassword" ; system.out.println('
' + ' : tohexstring(getsha(string1))); string2="hashtrial" tohexstring(getsha(string2))); catch (nosuchalgorithmexception e) system.out.println('exception thrown for incorrect algorithm: e); < pre> <p> <strong>Output:</strong> </p> <pre> myPassword : 450ad03db9395dfccb5e03066fd7f16cfba2b61e23d516373714471459052ec90a9a4bf3a151e600ea8aaed36e3b8c21a3d38ab1705839749d130da4380f1448 hashtrial : 9520ea1a8d60d23334e6d59acebd587de6fec1e53db5836f467096c540ae60f7c85e9fbc90856dee9d6563609b8786b03b47892af0bad44bdcab2206f22df5cb </pre> <p>The above code uses the instance of <strong> <em>MessageDigest</em> </strong> class to generate a hash for <strong> <em>SHA512</em> </strong> . The SHA512 returns a byte array that needs to be converted into a readable hexadecimal format. And lastly, the encrypted hash value is displayed.</p> <h3>Password-Based Encryption using Salt and Base64:</h3> <p>The password-based encryption technique uses plain text passwords and salt values to generate a hash value. And the hash value is then encoded as a Base64 string. Salt value contains random data generated using an instance of Random class from java.util package.</p> <p>The following program demonstrates password encryption using salt and base64.</p> <p> <strong>PassEncTech4.java</strong> </p> <pre> import java.security.NoSuchAlgorithmException; import java.security.SecureRandom; import java.security.spec.InvalidKeySpecException; import java.util.Arrays; import java.util.Base64; import java.util.Random; import javax.crypto.SecretKeyFactory; import javax.crypto.spec.PBEKeySpec; public class PassEncTech4 { /* Driver Code */ public static void main(String[] args) { /* Plain text Password. */ String password = &apos;myNewPass123&apos;; /* generates the Salt value. It can be stored in a database. */ String saltvalue = PassBasedEnc.getSaltvalue(30); /* generates an encrypted password. It can be stored in a database.*/ String encryptedpassword = PassBasedEnc.generateSecurePassword(password, saltvalue); /* Print out plain text password, encrypted password and salt value. */ System.out.println(&apos;Plain text password = &apos; + password); System.out.println(&apos;Secure password = &apos; + encryptedpassword); System.out.println(&apos;Salt value = &apos; + saltvalue); /* verify the original password and encrypted password */ Boolean status = PassBasedEnc.verifyUserPassword(password,encryptedpassword,saltvalue); if(status==true) System.out.println(&apos;Password Matched!!&apos;); else System.out.println(&apos;Password Mismatched&apos;); } } class PassBasedEnc { /* Declaration of variables */ private static final Random random = new SecureRandom(); private static final String characters = &apos;0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz&apos;; private static final int iterations = 10000; private static final int keylength = 256; /* Method to generate the salt value. */ public static String getSaltvalue(int length) { StringBuilder finalval = new StringBuilder(length); for (int i = 0; i <length; i++) { finalval.append(characters.charat(random.nextint(characters.length()))); } return new string(finalval); * method to generate the hash value public static byte[] hash(char[] password, salt) pbekeyspec spec="new" pbekeyspec(password, salt, iterations, keylength); arrays.fill(password, character.min_value); try secretkeyfactory skf="SecretKeyFactory.getInstance(&apos;PBKDF2WithHmacSHA1&apos;);" skf.generatesecret(spec).getencoded(); catch (nosuchalgorithmexception | invalidkeyspecexception e) throw assertionerror('error while hashing a password: ' + e.getmessage(), e); finally spec.clearpassword(); encrypt password using original and salt value. string generatesecurepassword(string finalval="null;" securepassword="hash(password.toCharArray()," salt.getbytes()); finalval; verify if both matches or not boolean verifyuserpassword(string providedpassword, securedpassword, secure with same newsecurepassword="generateSecurePassword(providedPassword," salt); check two passwords are equal < pre> <p> <strong>Output:</strong> </p> <pre> Plain text password = myNewPass123 Secure password = sA0jNGQTrAfMUiqrB++bMKTU55ThdFCl16ZZTIXwD2M= Salt value = n7d9MPQFXxDqzT6onmong3hQt8Nyko Password Matched!! </pre> <p>In the above code, two classes are defined.</p> <ol class="points"> <li>The class <strong> <em>PassEncTech4</em> </strong> contains the driver code for the program. It generates a salt value and encrypted password using the given plain-text password. And verifies them using the value returned by the <strong> <em>verifyUserPassword() </em> </strong> </li> <li>In the class <strong> <em>PassBasedEnc, </em> </strong> 4 methods are defined. The first method is <strong> <em>getSaltvalue()</em> </strong> which generates the value using <strong> <em>Random</em> </strong> class from <strong> <em>util</em> </strong> package. Then <strong> <em>hash()</em> </strong> is defined that has a return type of byte array. The <strong> <em>generateSecurePassword() </em> </strong> uses plain-text password and salt value with the <strong> <em>hash()</em> </strong> method. And lastly, the two passwords are matched using the <strong> <em>verifyUserPassword()</em> </strong> method.</li> </ol> <h2>Techniques for Cracking the Hash</h2> <p>A hash value is prone to different kinds of attacks by attackers. Some of them are mentioned below,</p> <ol class="points"> <tr><td>Brute force attack:</td> In the brute force attack, the attacker submits multiple combinations of passphrases or passwords in the hope that one of the combinations will match and he can enter into the system. <br> To avoid this kind of attack the passphrase should use a combination of alphabets, numbers and symbols. Another way is to set a fixed number of invalid attempts and after that ask for human verification like a captcha. </tr><tr><td>Dictionary attack:</td> Dictionary attack is an enhanced version of brute force attack. In this technique, the encrypted cipher is tried to be decrypted using multiple possibilities, like the words in a dictionary. </tr><tr><td>Rainbow tables:</td> The technique is about a rainbow table that is precomputed table for reversing the cryptographic hash functions. The rainbow tables are used to discover the plain text passwords up to a certain length and a limited number of characters. So it uses a side-loop table in order to reduce the storage usage and increase the speed of attack. </tr></ol> <hr></length;></pre></32)></pre></32)></pre></bytes.length>

يوضح الكود أعلاه تنفيذ رسالة دايجست فئة في java.security طَرد. يُرجع MD5 مصفوفة بايت تحتاج إلى تحويلها إلى تنسيق سداسي عشري قابل للقراءة.

تتميز تقنية التجزئة MD5 بأنها سهلة وسريعة التنفيذ ولكنها أيضًا عرضة لهجمات القوة الغاشمة أو هجمات القاموس.

SHA256

SHA هي خوارزمية التجزئة الآمنة. يستخدم وظيفة تشفير تأخذ كلمة المرور ذات النص العادي 32 بت وتحولها إلى قيمة تجزئة ذات حجم ثابت 256 بت. يتم تنفيذ تقنية التجزئة هذه باستخدام فئة messageDiagest لحزمة java.security.

إنها تقنية تشفير أحادية الاتجاه. بمجرد تشفير عبارة المرور، لا يمكن فك تشفيرها مرة أخرى.

PassEncTech2.java

 import java.math.BigInteger; import java.nio.charset.StandardCharsets; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; public class PassEncTech2 { public static byte[] getSHA(String input) throws NoSuchAlgorithmException { /* MessageDigest instance for hashing using SHA256 */ MessageDigest md = MessageDigest.getInstance(&apos;SHA-256&apos;); /* digest() method called to calculate message digest of an input and return array of byte */ return md.digest(input.getBytes(StandardCharsets.UTF_8)); } public static String toHexString(byte[] hash) { /* Convert byte array of hash into digest */ BigInteger number = new BigInteger(1, hash); /* Convert the digest into hex value */ StringBuilder hexString = new StringBuilder(number.toString(16)); /* Pad with leading zeros */ while (hexString.length() <32) { hexstring.insert(0, \'0\'); } return hexstring.tostring(); * driver code public static void main(string args[]) try string string1="myPassword" ; system.out.println(\'
\' + \' : tohexstring(getsha(string1))); string2="hashtrial" tohexstring(getsha(string2))); catch (nosuchalgorithmexception e) system.out.println(\'exception thrown for incorrect algorithm: e); < pre> <p> <strong>Output:</strong> </p> <pre> myPassword : 76549b827ec46e705fd03831813fa52172338f0dfcbd711ed44b81a96dac51c6 hashtrial : d3e3224a59d69e9a000f1ce6782cb6a8be1eb3155610ff41bffbcbc95adc5d7 </pre> <p>The above code uses the instance of <strong> <em>MessageDigest</em> </strong> class to generate a hash for <strong> <em>SHA256</em> </strong> . The SHA256 returns a byte array that needs to be converted into a readable hexadecimal format. And lastly, the encrypted hash value is displayed.</p> <h3>SHA512 MD5 Hashing Technique</h3> <p>SHA512 uses a cryptographic function that takes up the 64-bit plain-text password and converts it into a fixed size 512-bit hash value. This hashing technique is also implemented using the MessageDiagest class of java.security package.</p> <p> <strong>PassEncTech2.java</strong> </p> <pre> import java.math.BigInteger; import java.nio.charset.StandardCharsets; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; public class PassEncTech2 { public static byte[] getSHA(String input) throws NoSuchAlgorithmException { /* MessageDigest instance for hashing using SHA512*/ MessageDigest md = MessageDigest.getInstance(&apos;SHA-512&apos;); /* digest() method called to calculate message digest of an input and return array of byte */ return md.digest(input.getBytes(StandardCharsets.UTF_8)); } public static String toHexString(byte[] hash) { /* Convert byte array of hash into digest */ BigInteger number = new BigInteger(1, hash); /* Convert the digest into hex value */ StringBuilder hexString = new StringBuilder(number.toString(16)); /* Pad with leading zeros */ while (hexString.length() <32) { hexstring.insert(0, \'0\'); } return hexstring.tostring(); * driver code public static void main(string args[]) try string string1="myPassword" ; system.out.println(\'
\' + \' : tohexstring(getsha(string1))); string2="hashtrial" tohexstring(getsha(string2))); catch (nosuchalgorithmexception e) system.out.println(\'exception thrown for incorrect algorithm: e); < pre> <p> <strong>Output:</strong> </p> <pre> myPassword : 450ad03db9395dfccb5e03066fd7f16cfba2b61e23d516373714471459052ec90a9a4bf3a151e600ea8aaed36e3b8c21a3d38ab1705839749d130da4380f1448 hashtrial : 9520ea1a8d60d23334e6d59acebd587de6fec1e53db5836f467096c540ae60f7c85e9fbc90856dee9d6563609b8786b03b47892af0bad44bdcab2206f22df5cb </pre> <p>The above code uses the instance of <strong> <em>MessageDigest</em> </strong> class to generate a hash for <strong> <em>SHA512</em> </strong> . The SHA512 returns a byte array that needs to be converted into a readable hexadecimal format. And lastly, the encrypted hash value is displayed.</p> <h3>Password-Based Encryption using Salt and Base64:</h3> <p>The password-based encryption technique uses plain text passwords and salt values to generate a hash value. And the hash value is then encoded as a Base64 string. Salt value contains random data generated using an instance of Random class from java.util package.</p> <p>The following program demonstrates password encryption using salt and base64.</p> <p> <strong>PassEncTech4.java</strong> </p> <pre> import java.security.NoSuchAlgorithmException; import java.security.SecureRandom; import java.security.spec.InvalidKeySpecException; import java.util.Arrays; import java.util.Base64; import java.util.Random; import javax.crypto.SecretKeyFactory; import javax.crypto.spec.PBEKeySpec; public class PassEncTech4 { /* Driver Code */ public static void main(String[] args) { /* Plain text Password. */ String password = &apos;myNewPass123&apos;; /* generates the Salt value. It can be stored in a database. */ String saltvalue = PassBasedEnc.getSaltvalue(30); /* generates an encrypted password. It can be stored in a database.*/ String encryptedpassword = PassBasedEnc.generateSecurePassword(password, saltvalue); /* Print out plain text password, encrypted password and salt value. */ System.out.println(&apos;Plain text password = &apos; + password); System.out.println(&apos;Secure password = &apos; + encryptedpassword); System.out.println(&apos;Salt value = &apos; + saltvalue); /* verify the original password and encrypted password */ Boolean status = PassBasedEnc.verifyUserPassword(password,encryptedpassword,saltvalue); if(status==true) System.out.println(&apos;Password Matched!!&apos;); else System.out.println(&apos;Password Mismatched&apos;); } } class PassBasedEnc { /* Declaration of variables */ private static final Random random = new SecureRandom(); private static final String characters = &apos;0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz&apos;; private static final int iterations = 10000; private static final int keylength = 256; /* Method to generate the salt value. */ public static String getSaltvalue(int length) { StringBuilder finalval = new StringBuilder(length); for (int i = 0; i <length; i++) { finalval.append(characters.charat(random.nextint(characters.length()))); } return new string(finalval); * method to generate the hash value public static byte[] hash(char[] password, salt) pbekeyspec spec="new" pbekeyspec(password, salt, iterations, keylength); arrays.fill(password, character.min_value); try secretkeyfactory skf="SecretKeyFactory.getInstance(&apos;PBKDF2WithHmacSHA1&apos;);" skf.generatesecret(spec).getencoded(); catch (nosuchalgorithmexception | invalidkeyspecexception e) throw assertionerror(\'error while hashing a password: \' + e.getmessage(), e); finally spec.clearpassword(); encrypt password using original and salt value. string generatesecurepassword(string finalval="null;" securepassword="hash(password.toCharArray()," salt.getbytes()); finalval; verify if both matches or not boolean verifyuserpassword(string providedpassword, securedpassword, secure with same newsecurepassword="generateSecurePassword(providedPassword," salt); check two passwords are equal < pre> <p> <strong>Output:</strong> </p> <pre> Plain text password = myNewPass123 Secure password = sA0jNGQTrAfMUiqrB++bMKTU55ThdFCl16ZZTIXwD2M= Salt value = n7d9MPQFXxDqzT6onmong3hQt8Nyko Password Matched!! </pre> <p>In the above code, two classes are defined.</p> <ol class="points"> <li>The class <strong> <em>PassEncTech4</em> </strong> contains the driver code for the program. It generates a salt value and encrypted password using the given plain-text password. And verifies them using the value returned by the <strong> <em>verifyUserPassword() </em> </strong> </li> <li>In the class <strong> <em>PassBasedEnc, </em> </strong> 4 methods are defined. The first method is <strong> <em>getSaltvalue()</em> </strong> which generates the value using <strong> <em>Random</em> </strong> class from <strong> <em>util</em> </strong> package. Then <strong> <em>hash()</em> </strong> is defined that has a return type of byte array. The <strong> <em>generateSecurePassword() </em> </strong> uses plain-text password and salt value with the <strong> <em>hash()</em> </strong> method. And lastly, the two passwords are matched using the <strong> <em>verifyUserPassword()</em> </strong> method.</li> </ol> <h2>Techniques for Cracking the Hash</h2> <p>A hash value is prone to different kinds of attacks by attackers. Some of them are mentioned below,</p> <ol class="points"> <tr><td>Brute force attack:</td> In the brute force attack, the attacker submits multiple combinations of passphrases or passwords in the hope that one of the combinations will match and he can enter into the system. <br> To avoid this kind of attack the passphrase should use a combination of alphabets, numbers and symbols. Another way is to set a fixed number of invalid attempts and after that ask for human verification like a captcha. </tr><tr><td>Dictionary attack:</td> Dictionary attack is an enhanced version of brute force attack. In this technique, the encrypted cipher is tried to be decrypted using multiple possibilities, like the words in a dictionary. </tr><tr><td>Rainbow tables:</td> The technique is about a rainbow table that is precomputed table for reversing the cryptographic hash functions. The rainbow tables are used to discover the plain text passwords up to a certain length and a limited number of characters. So it uses a side-loop table in order to reduce the storage usage and increase the speed of attack. </tr></ol> <hr></length;></pre></32)></pre></32)>

يستخدم الكود أعلاه مثيل رسالة دايجست فئة لإنشاء تجزئة ل SHA256 . يُرجع SHA256 مصفوفة بايت تحتاج إلى تحويلها إلى تنسيق سداسي عشري قابل للقراءة. وأخيرًا، يتم عرض قيمة التجزئة المشفرة.

تقنية التجزئة SHA512 MD5

يستخدم SHA512 وظيفة تشفير تأخذ كلمة المرور ذات النص العادي 64 بت وتحولها إلى قيمة تجزئة ذات حجم ثابت 512 بت. يتم أيضًا تنفيذ تقنية التجزئة هذه باستخدام فئة messageDiagest الخاصة بحزمة java.security.

PassEncTech2.java

 import java.math.BigInteger; import java.nio.charset.StandardCharsets; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; public class PassEncTech2 { public static byte[] getSHA(String input) throws NoSuchAlgorithmException { /* MessageDigest instance for hashing using SHA512*/ MessageDigest md = MessageDigest.getInstance(&apos;SHA-512&apos;); /* digest() method called to calculate message digest of an input and return array of byte */ return md.digest(input.getBytes(StandardCharsets.UTF_8)); } public static String toHexString(byte[] hash) { /* Convert byte array of hash into digest */ BigInteger number = new BigInteger(1, hash); /* Convert the digest into hex value */ StringBuilder hexString = new StringBuilder(number.toString(16)); /* Pad with leading zeros */ while (hexString.length() <32) { hexstring.insert(0, \'0\'); } return hexstring.tostring(); * driver code public static void main(string args[]) try string string1="myPassword" ; system.out.println(\'
\' + \' : tohexstring(getsha(string1))); string2="hashtrial" tohexstring(getsha(string2))); catch (nosuchalgorithmexception e) system.out.println(\'exception thrown for incorrect algorithm: e); < pre> <p> <strong>Output:</strong> </p> <pre> myPassword : 450ad03db9395dfccb5e03066fd7f16cfba2b61e23d516373714471459052ec90a9a4bf3a151e600ea8aaed36e3b8c21a3d38ab1705839749d130da4380f1448 hashtrial : 9520ea1a8d60d23334e6d59acebd587de6fec1e53db5836f467096c540ae60f7c85e9fbc90856dee9d6563609b8786b03b47892af0bad44bdcab2206f22df5cb </pre> <p>The above code uses the instance of <strong> <em>MessageDigest</em> </strong> class to generate a hash for <strong> <em>SHA512</em> </strong> . The SHA512 returns a byte array that needs to be converted into a readable hexadecimal format. And lastly, the encrypted hash value is displayed.</p> <h3>Password-Based Encryption using Salt and Base64:</h3> <p>The password-based encryption technique uses plain text passwords and salt values to generate a hash value. And the hash value is then encoded as a Base64 string. Salt value contains random data generated using an instance of Random class from java.util package.</p> <p>The following program demonstrates password encryption using salt and base64.</p> <p> <strong>PassEncTech4.java</strong> </p> <pre> import java.security.NoSuchAlgorithmException; import java.security.SecureRandom; import java.security.spec.InvalidKeySpecException; import java.util.Arrays; import java.util.Base64; import java.util.Random; import javax.crypto.SecretKeyFactory; import javax.crypto.spec.PBEKeySpec; public class PassEncTech4 { /* Driver Code */ public static void main(String[] args) { /* Plain text Password. */ String password = &apos;myNewPass123&apos;; /* generates the Salt value. It can be stored in a database. */ String saltvalue = PassBasedEnc.getSaltvalue(30); /* generates an encrypted password. It can be stored in a database.*/ String encryptedpassword = PassBasedEnc.generateSecurePassword(password, saltvalue); /* Print out plain text password, encrypted password and salt value. */ System.out.println(&apos;Plain text password = &apos; + password); System.out.println(&apos;Secure password = &apos; + encryptedpassword); System.out.println(&apos;Salt value = &apos; + saltvalue); /* verify the original password and encrypted password */ Boolean status = PassBasedEnc.verifyUserPassword(password,encryptedpassword,saltvalue); if(status==true) System.out.println(&apos;Password Matched!!&apos;); else System.out.println(&apos;Password Mismatched&apos;); } } class PassBasedEnc { /* Declaration of variables */ private static final Random random = new SecureRandom(); private static final String characters = &apos;0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz&apos;; private static final int iterations = 10000; private static final int keylength = 256; /* Method to generate the salt value. */ public static String getSaltvalue(int length) { StringBuilder finalval = new StringBuilder(length); for (int i = 0; i <length; i++) { finalval.append(characters.charat(random.nextint(characters.length()))); } return new string(finalval); * method to generate the hash value public static byte[] hash(char[] password, salt) pbekeyspec spec="new" pbekeyspec(password, salt, iterations, keylength); arrays.fill(password, character.min_value); try secretkeyfactory skf="SecretKeyFactory.getInstance(&apos;PBKDF2WithHmacSHA1&apos;);" skf.generatesecret(spec).getencoded(); catch (nosuchalgorithmexception | invalidkeyspecexception e) throw assertionerror(\'error while hashing a password: \' + e.getmessage(), e); finally spec.clearpassword(); encrypt password using original and salt value. string generatesecurepassword(string finalval="null;" securepassword="hash(password.toCharArray()," salt.getbytes()); finalval; verify if both matches or not boolean verifyuserpassword(string providedpassword, securedpassword, secure with same newsecurepassword="generateSecurePassword(providedPassword," salt); check two passwords are equal < pre> <p> <strong>Output:</strong> </p> <pre> Plain text password = myNewPass123 Secure password = sA0jNGQTrAfMUiqrB++bMKTU55ThdFCl16ZZTIXwD2M= Salt value = n7d9MPQFXxDqzT6onmong3hQt8Nyko Password Matched!! </pre> <p>In the above code, two classes are defined.</p> <ol class="points"> <li>The class <strong> <em>PassEncTech4</em> </strong> contains the driver code for the program. It generates a salt value and encrypted password using the given plain-text password. And verifies them using the value returned by the <strong> <em>verifyUserPassword() </em> </strong> </li> <li>In the class <strong> <em>PassBasedEnc, </em> </strong> 4 methods are defined. The first method is <strong> <em>getSaltvalue()</em> </strong> which generates the value using <strong> <em>Random</em> </strong> class from <strong> <em>util</em> </strong> package. Then <strong> <em>hash()</em> </strong> is defined that has a return type of byte array. The <strong> <em>generateSecurePassword() </em> </strong> uses plain-text password and salt value with the <strong> <em>hash()</em> </strong> method. And lastly, the two passwords are matched using the <strong> <em>verifyUserPassword()</em> </strong> method.</li> </ol> <h2>Techniques for Cracking the Hash</h2> <p>A hash value is prone to different kinds of attacks by attackers. Some of them are mentioned below,</p> <ol class="points"> <tr><td>Brute force attack:</td> In the brute force attack, the attacker submits multiple combinations of passphrases or passwords in the hope that one of the combinations will match and he can enter into the system. <br> To avoid this kind of attack the passphrase should use a combination of alphabets, numbers and symbols. Another way is to set a fixed number of invalid attempts and after that ask for human verification like a captcha. </tr><tr><td>Dictionary attack:</td> Dictionary attack is an enhanced version of brute force attack. In this technique, the encrypted cipher is tried to be decrypted using multiple possibilities, like the words in a dictionary. </tr><tr><td>Rainbow tables:</td> The technique is about a rainbow table that is precomputed table for reversing the cryptographic hash functions. The rainbow tables are used to discover the plain text passwords up to a certain length and a limited number of characters. So it uses a side-loop table in order to reduce the storage usage and increase the speed of attack. </tr></ol> <hr></length;></pre></32)>

يستخدم الكود أعلاه مثيل رسالة دايجست فئة لإنشاء تجزئة ل SHA512 . يُرجع SHA512 مصفوفة بايت تحتاج إلى تحويلها إلى تنسيق سداسي عشري قابل للقراءة. وأخيرًا، يتم عرض قيمة التجزئة المشفرة.

التشفير المعتمد على كلمة المرور باستخدام Salt وBase64:

تستخدم تقنية التشفير المبني على كلمة المرور كلمات مرور نصية عادية وقيم ملحية لإنشاء قيمة التجزئة. ويتم بعد ذلك ترميز قيمة التجزئة كسلسلة Base64. تحتوي قيمة الملح على بيانات عشوائية تم إنشاؤها باستخدام مثيل للفئة العشوائية من حزمة java.util.

يوضح البرنامج التالي تشفير كلمة المرور باستخدام salt وbase64.

PassEncTech4.java

 import java.security.NoSuchAlgorithmException; import java.security.SecureRandom; import java.security.spec.InvalidKeySpecException; import java.util.Arrays; import java.util.Base64; import java.util.Random; import javax.crypto.SecretKeyFactory; import javax.crypto.spec.PBEKeySpec; public class PassEncTech4 { /* Driver Code */ public static void main(String[] args) { /* Plain text Password. */ String password = &apos;myNewPass123&apos;; /* generates the Salt value. It can be stored in a database. */ String saltvalue = PassBasedEnc.getSaltvalue(30); /* generates an encrypted password. It can be stored in a database.*/ String encryptedpassword = PassBasedEnc.generateSecurePassword(password, saltvalue); /* Print out plain text password, encrypted password and salt value. */ System.out.println(&apos;Plain text password = &apos; + password); System.out.println(&apos;Secure password = &apos; + encryptedpassword); System.out.println(&apos;Salt value = &apos; + saltvalue); /* verify the original password and encrypted password */ Boolean status = PassBasedEnc.verifyUserPassword(password,encryptedpassword,saltvalue); if(status==true) System.out.println(&apos;Password Matched!!&apos;); else System.out.println(&apos;Password Mismatched&apos;); } } class PassBasedEnc { /* Declaration of variables */ private static final Random random = new SecureRandom(); private static final String characters = &apos;0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz&apos;; private static final int iterations = 10000; private static final int keylength = 256; /* Method to generate the salt value. */ public static String getSaltvalue(int length) { StringBuilder finalval = new StringBuilder(length); for (int i = 0; i <length; i++) { finalval.append(characters.charat(random.nextint(characters.length()))); } return new string(finalval); * method to generate the hash value public static byte[] hash(char[] password, salt) pbekeyspec spec="new" pbekeyspec(password, salt, iterations, keylength); arrays.fill(password, character.min_value); try secretkeyfactory skf="SecretKeyFactory.getInstance(&apos;PBKDF2WithHmacSHA1&apos;);" skf.generatesecret(spec).getencoded(); catch (nosuchalgorithmexception | invalidkeyspecexception e) throw assertionerror(\\'error while hashing a password: \\' + e.getmessage(), e); finally spec.clearpassword(); encrypt password using original and salt value. string generatesecurepassword(string finalval="null;" securepassword="hash(password.toCharArray()," salt.getbytes()); finalval; verify if both matches or not boolean verifyuserpassword(string providedpassword, securedpassword, secure with same newsecurepassword="generateSecurePassword(providedPassword," salt); check two passwords are equal < pre> <p> <strong>Output:</strong> </p> <pre> Plain text password = myNewPass123 Secure password = sA0jNGQTrAfMUiqrB++bMKTU55ThdFCl16ZZTIXwD2M= Salt value = n7d9MPQFXxDqzT6onmong3hQt8Nyko Password Matched!! </pre> <p>In the above code, two classes are defined.</p> <ol class="points"> <li>The class <strong> <em>PassEncTech4</em> </strong> contains the driver code for the program. It generates a salt value and encrypted password using the given plain-text password. And verifies them using the value returned by the <strong> <em>verifyUserPassword() </em> </strong> </li> <li>In the class <strong> <em>PassBasedEnc, </em> </strong> 4 methods are defined. The first method is <strong> <em>getSaltvalue()</em> </strong> which generates the value using <strong> <em>Random</em> </strong> class from <strong> <em>util</em> </strong> package. Then <strong> <em>hash()</em> </strong> is defined that has a return type of byte array. The <strong> <em>generateSecurePassword() </em> </strong> uses plain-text password and salt value with the <strong> <em>hash()</em> </strong> method. And lastly, the two passwords are matched using the <strong> <em>verifyUserPassword()</em> </strong> method.</li> </ol> <h2>Techniques for Cracking the Hash</h2> <p>A hash value is prone to different kinds of attacks by attackers. Some of them are mentioned below,</p> <ol class="points"> <tr><td>Brute force attack:</td> In the brute force attack, the attacker submits multiple combinations of passphrases or passwords in the hope that one of the combinations will match and he can enter into the system. <br> To avoid this kind of attack the passphrase should use a combination of alphabets, numbers and symbols. Another way is to set a fixed number of invalid attempts and after that ask for human verification like a captcha. </tr><tr><td>Dictionary attack:</td> Dictionary attack is an enhanced version of brute force attack. In this technique, the encrypted cipher is tried to be decrypted using multiple possibilities, like the words in a dictionary. </tr><tr><td>Rainbow tables:</td> The technique is about a rainbow table that is precomputed table for reversing the cryptographic hash functions. The rainbow tables are used to discover the plain text passwords up to a certain length and a limited number of characters. So it uses a side-loop table in order to reduce the storage usage and increase the speed of attack. </tr></ol> <hr></length;>

في الكود أعلاه، تم تعريف فئتين.

1. الفصل باس إنك تيك 4 يحتوي على رمز التشغيل الخاص بالبرنامج. يقوم بإنشاء قيمة ملح وكلمة مرور مشفرة باستخدام كلمة مرور النص العادي المحددة. والتحقق منها باستخدام القيمة التي أرجعها ملف التحقق من كلمة المرور ()
2. في الفصل باسباسيد إنك, تم تحديد 4 طرق. الطريقة الأولى هي الحصول على قيمة الملح () الذي يولد القيمة باستخدام عشوائي فئة من util طَرد. ثم التجزئة () تم تعريفه بأنه يحتوي على نوع إرجاع لمصفوفة البايت. ال إنشاء كلمة مرور آمنة () يستخدم كلمة مرور نصية عادية وقيمة ملحية مع ملف التجزئة () طريقة. وأخيرًا، تتم مطابقة كلمتي المرور باستخدام التحقق من كلمة المرور () طريقة.

تقنيات تكسير التجزئة

تكون قيمة التجزئة عرضة لأنواع مختلفة من الهجمات من قبل المهاجمين. بعض منها مذكورة أدناه ،

هجوم القوة الغاشمة:في هجوم القوة الغاشمة، يرسل المهاجم مجموعات متعددة من عبارات المرور أو كلمات المرور على أمل أن تتطابق إحدى المجموعات ويمكنه الدخول إلى النظام.
لتجنب هذا النوع من الهجمات، يجب أن تستخدم عبارة المرور مجموعة من الحروف الهجائية والأرقام والرموز. هناك طريقة أخرى وهي تعيين عدد ثابت من المحاولات غير الصالحة وبعد ذلك طلب التحقق البشري مثل كلمة التحقق.هجوم القاموس:هجوم القاموس هو نسخة محسنة من هجوم القوة الغاشمة. في هذه التقنية، تتم محاولة فك التشفير المشفر باستخدام إمكانيات متعددة، مثل الكلمات الموجودة في القاموس.طاولات قوس قزح:تدور هذه التقنية حول جدول قوس قزح وهو جدول محسوب مسبقًا لعكس وظائف تجزئة التشفير. تُستخدم جداول قوس قزح لاكتشاف كلمات مرور النص العادي التي يصل طولها إلى حد معين وعدد محدود من الأحرف. لذلك فهو يستخدم جدول حلقة جانبية لتقليل استخدام التخزين وزيادة سرعة الهجوم.