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Generate HMAC using SHA256 in Scala
import javax.crypto.Mac
import javax.crypto.spec.SecretKeySpec
Object HMACgen {
def generateHMAC(sharedSecret: String, preHashString: String): String = {
val secret = new SecretKeySpec(sharedSecret.getBytes, "SHA256") //Crypto Funs : 'SHA256' , 'HmacSHA1'
val mac = Mac.getInstance("SHA256")
mac.init(secret)
val hashString: Array[Byte] = mac.doFinal(preHashString.getBytes)
new String(hashString.map(_.toChar))
}
}
@fernaspiazu
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fernaspiazu commented Feb 20, 2018

What value should have preHashString parameter? What does it mean?

@JesseChisholm
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JesseChisholm commented May 8, 2018

preHashString is just the data string you want to hash. It is often some agreed upon group of fields from the record this hashString will be attached to. Perhaps ...

record.hash = generateHMAC(sharedSecret, record.ip+record.lang+record.timestamp)

Then ship the completed record across the wire somewhere.

The receiver of this record can validate by recalculating the record.hash to see if it was made with the agreed upon sharedSecret key string.

@Uxito-Ada
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Uxito-Ada commented Feb 10, 2022

The code in line 8
val mac = Mac.getInstance("SHA256")
does not work for me, which will raise an error like:
Exception in thread "main" java.security.NoSuchAlgorithmException: Algorithm SHA256 not available at javax.crypto.Mac.getInstance(Mac.java:181)
The feasible algorithm specification for me is like:
val mac = Mac.getInstance("HmacSHA256")

@codertitto
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codertitto commented Mar 2, 2022

is it possible to generateHMAC without a sharedSecret?

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