How to hash some string with sha256 in Java

Question

How can I hash some string with sha256 in Java  Does anybody know of any free library for this

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Another alternative is Guava which has an easy-to-use suite of Hashing utilities  For example  to hash a string using SHA256 as a hex-string you would simply do   final String hashed   Hashing sha256            hashString  your input   StandardCharsets UTF 8           toString

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I think that the easiest solution is to use Apache Common Codec   String sha256hex   org apache commons codec digest DigestUtils sha256Hex stringText

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In Java  MessageDigest class is used to calculate cryptographic hashing value  This class provides cryptographic hash function   MD5  SHA-1 and SHA-256  to find hash value of text   Code example for using SHA-256 algorithm   public void printHash String str  throws NoSuchAlgorithmException    MessageDigest md MessageDigest getInstance  SHA-256     byte   sha256 md digest str getBytes StandardCharsets UTF 8        for byte b   sha256          System out printf   02x  b

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private static String getMessageDigest String message  String algorithm     MessageDigest digest   try     digest   MessageDigest getInstance algorithm     byte data     digest digest message getBytes  UTF-8       return convertByteArrayToHexString data      catch  NoSuchAlgorithmException   UnsupportedEncodingException e         TODO Auto-generated catch block   e printStackTrace        return null      You can call above method with different algorithms like below   getMessageDigest message   MD5    getMessageDigest message   SHA-256    getMessageDigest message   SHA-1      You can refer this link for complete application

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SHA-256 isn t an  encoding  - it s a one-way hash   You d basically convert the string into bytes  e g  using text getBytes StandardCharsets UTF 8   and then hash the bytes  Note that the result of the hash would also be arbitrary binary data  and if you want to represent that in a string  you should use base64 or hex    don t try to use the String byte    String  constructor   e g   MessageDigest digest   MessageDigest getInstance  SHA-256    byte   hash   digest digest text getBytes StandardCharsets UTF 8

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If you are using Java 8 you can encode the byte   by doing  MessageDigest digest   MessageDigest getInstance  SHA-256    byte   hash   digest digest text getBytes StandardCharsets UTF 8    String encoded   Base64 getEncoder   encodeToString hash

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You can use MessageDigest in the following way   public static String getSHA256 String data       StringBuffer sb   new StringBuffer        try          MessageDigest md   MessageDigest getInstance  SHA-256            md update data getBytes             byte byteData     md digest             for  int i   0  i  lt  byteData length  i               sb append Integer toString  byteData i   amp  0xff    0x100  16  substring 1                    catch Exception e           e printStackTrace              return sb toString

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String hashWith256 String textToHash        MessageDigest digest   MessageDigest getInstance  SHA-256        byte   byteOfTextToHash   textToHash getBytes StandardCharsets UTF 8       byte   hashedByetArray   digest digest byteOfTextToHash       String encoded   Base64 getEncoder   encodeToString hashedByetArray       return encoded

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In Java 8  import java nio charset StandardCharsets  import java security MessageDigest  import java security NoSuchAlgorithmException  import java util Scanner  import javax xml bind DatatypeConverter    Scanner scanner   new Scanner System in   String password   scanner nextLine    scanner close     MessageDigest digest   null  try       digest   MessageDigest getInstance  SHA-256      catch  NoSuchAlgorithmException e           TODO Auto-generated catch block     e printStackTrace      byte   hash   digest digest password getBytes StandardCharsets UTF 8    String encoded   DatatypeConverter printHexBinary hash           System out println encoded toLowerCase

User · Answer

Here is a slightly more performant way to turn the digest into a hex string   private static final char   hexArray    0123456789abcdef  toCharArray     public static String getSHA256 String data        StringBuilder sb   new StringBuilder        try           MessageDigest md   MessageDigest getInstance  SHA-256            md update data getBytes             byte   byteData   md digest            sb append bytesToHex byteData         catch Exception e            e printStackTrace              return sb toString       private static String bytesToHex byte   bytes        char   hexChars   new char bytes length   2       for   int j   0  j  lt  bytes length  j               int v   bytes j   amp  0xFF          hexChars j   2    hexArray v  gt  gt  gt  4           hexChars j   2   1    hexArray v  amp  0x0F             return String valueOf hexChars       Does anyone know of a faster way in Java

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I traced the Apache code through DigestUtils and sha256 seems to default back to java security MessageDigest for calculation   Apache does not implement an independent sha256 solution   I was looking for an independent implementation to compare against the java security library   FYI only

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This is what i have been used for hashing   String pass    password    MessageDigest messageDigest   MessageDigest getInstance  SHA-256    byte hashBytes     messageDigest digest pass getBytes StandardCharsets UTF 8    BigInteger noHash   new BigInteger 1  hashBytes   String hashStr   noHash toString 16     Output  5e884898da28047151d0e56f8dc6292773603d0d6aabbdd62a11ef721d1542d8

User · Answer

Full example hash to string as another string   public static String sha256 String base        try          MessageDigest digest   MessageDigest getInstance  SHA-256            byte   hash   digest digest base getBytes  UTF-8             StringBuffer hexString   new StringBuffer             for  int i   0  i  lt  hash length  i                  String hex   Integer toHexString 0xff  amp  hash i                if hex length      1  hexString append  0                hexString append hex                      return hexString toString          catch Exception ex          throw new RuntimeException ex

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import java security MessageDigest   public class CodeSnippets     public static String getSha256 String value        try          MessageDigest md   MessageDigest getInstance  SHA-256            md update value getBytes             return bytesToHex md digest           catch Exception ex           throw new RuntimeException ex             private static String bytesToHex byte   bytes        StringBuffer result   new StringBuffer        for  byte b   bytes  result append Integer toString  b  amp  0xff    0x100  16  substring 1        return result toString

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This was my approach using Kotlin   private fun getHashFromEmailString email   String    String      val charset   Charsets UTF 8     val byteArray   email toByteArray charset      val digest   MessageDigest getInstance  SHA-256       val hash   digest digest byteArray       return hash fold       str  it - gt  str     02x  format it

[java] How to hash some string with sha256 in Java?

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