Fiecare aplicație software necesită un nume de utilizator și o parolă pentru a autentifica utilizatorul valid. Un nume de utilizator poate fi ceva asemănător unui ID de e-mail sau doar o combinație de caractere. Dar atunci când creați o parolă, trebuie să fiți foarte atenți. Pentru că oricine are acreditări valide poate intra în sistem și poate accesa informațiile.

Necesitatea criptării unei parole

Când un utilizator își setează parola, aceasta se stochează în baza de date ca text simplu. Stocarea textului simplu așa cum este în baza de date nu este deloc sigură. Hackerii pot sparge sistemul și fura parolele din baza de date.

Pentru a asigura securitatea parolei utilizatorului, aceasta este criptată folosind diferite tehnici de criptare. Folosind diverse tehnici de criptare, parola text simplu este stocată într-o formă criptată în baza de date. Există multe metode care pot fi folosite pentru a cripta parola. Dar hashingul este una dintre cele mai populare tehnici de criptare.

Tehnici Java Secure Hashing

Valoarea hash criptată este generată folosind anumiți algoritmi pe parola text simplu furnizată de utilizator. Programarea Java acceptă mai multe tehnici de hashing pentru a cripta o parolă.

dormi in js

Tehnica de hashing MD5

MD5 (Message Digest) este un algoritm de hashing foarte popular. Este o funcție hash criptografică care generează o valoare hash de 128 de biți. Acest algoritm este definit în pachetul java.security în programarea 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>

Codul de mai sus arată implementarea MessageDigest clasa in java.securitate pachet. MD5 returnează o matrice de octeți care trebuie convertită într-un format hexazecimal care poate fi citit.

applet

Tehnica de hashing MD5 este ușor și rapid de implementat, dar este, de asemenea, predispusă la atacuri de forță brută sau atacuri de dicționar.

SHA256

SHA este algoritmul Secure Hash. Utilizează o funcție criptografică care preia parola de text simplu de 32 de biți și o convertește într-o valoare hash de 256 de biți de dimensiune fixă. Această tehnică de hashing este implementată folosind clasa MessageDiagest a pachetului java.security.

Este o tehnică de criptare unidirecțională. Odată ce fraza de acces este criptată, nu poate fi decriptată înapoi.

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)>

Codul de mai sus folosește instanța de MessageDigest clasa pentru a genera un hash pentru SHA256 . SHA256 returnează o matrice de octeți care trebuie convertită într-un format hexazecimal care poate fi citit. Și, în sfârșit, este afișată valoarea hash criptată.

10 milioane

SHA512 MD5 Tehnica de hashing

SHA512 utilizează o funcție criptografică care preia parola de text simplu de 64 de biți și o convertește într-o valoare hash de 512 biți de dimensiune fixă. Această tehnică de hashing este implementată și folosind clasa MessageDiagest a pachetului 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)>

Codul de mai sus folosește instanța de MessageDigest clasa pentru a genera un hash pentru SHA512 . SHA512 returnează o matrice de octeți care trebuie convertită într-un format hexazecimal care poate fi citit. Și, în sfârșit, este afișată valoarea hash criptată.

Criptare bazată pe parolă folosind Salt și Base64:

Tehnica de criptare bazată pe parole utilizează parole cu text simplu și valori de sare pentru a genera o valoare hash. Și valoarea hash este apoi codificată ca șir Base64. Valoarea Salt conține date aleatorii generate folosind o instanță a clasei Random din pachetul java.util.

Următorul program demonstrează criptarea parolei folosind salt și base64.

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;>

În codul de mai sus, sunt definite două clase.

1. Clasa PassEncTech4 conține codul de driver pentru program. Acesta generează o valoare de sare și o parolă criptată folosind parola de text simplu dată. Și le verifică folosind valoarea returnată de verifyUserPassword()
2. În clasă PassBasedEnc, Sunt definite 4 metode. Prima metodă este getSaltvalue() care generează valoarea utilizând Aleatoriu clasa de la util pachet. Apoi hash() este definit care are un tip de returnare de matrice de octeți. The generateSecurePassword() folosește parola în text simplu și valoarea de sare cu hash() metodă. Și, în sfârșit, cele două parole sunt potrivite folosind verifyUserPassword() metodă.

Tehnici pentru spargerea hașului

O valoare hash este predispusă la diferite tipuri de atacuri din partea atacatorilor. Unele dintre ele sunt menționate mai jos,

setați delimitator java

Atacul de forță brută:În atacul cu forță brută, atacatorul trimite mai multe combinații de fraze de acces sau parole în speranța că una dintre combinații se va potrivi și poate intra în sistem.
Pentru a evita acest tip de atac, fraza de acces ar trebui să folosească o combinație de alfabete, numere și simboluri. O altă modalitate este să setați un număr fix de încercări nevalide și după aceea să cereți verificarea umană ca un captcha.Dicţionar atac:Atacul de dicționar este o versiune îmbunătățită a atacului cu forță brută. În această tehnică, cifrul criptat este încercat să fie decriptat folosind mai multe posibilități, precum cuvintele dintr-un dicționar.Mese curcubeu:Tehnica este despre un tabel curcubeu care este un tabel precalculat pentru inversarea funcțiilor hash criptografice. Tabelele curcubeu sunt folosite pentru a descoperi parolele cu text simplu până la o anumită lungime și un număr limitat de caractere. Deci folosește un tabel cu bucle laterale pentru a reduce utilizarea stocării și pentru a crește viteza de atac.