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I am implementing a basic encryption/decryption set of functions in nodejs and I keep getting the following error in the decryption part:
Error: Unsupported state or unable to authenticate data

This is my code so far:

import crypto from 'crypto'
import logger from './logger'

const ALGORITHM = 'aes-256-gcm'

export const encrypt = (keyBuffer, dataBuffer, aadBuffer) => 
 // iv stands for "initialization vector"
 const iv = Buffer.from(crypto.randomBytes(12), 'utf8')
 logger.debug('iv: ', iv)
 const encryptor = crypto.createCipheriv(ALGORITHM, keyBuffer, iv)
 logger.debug('encryptor: ', encryptor)
 logger.debug('dataBuffer: ', dataBuffer)
 return Buffer.concat([iv, encryptor.update(dataBuffer, 'utf8'), encryptor.final()])


export const decrypt = (keyBuffer, dataBuffer, aadBuffer) => 
 const iv = dataBuffer.slice(0, 96)

 const decryptor = crypto.createDecipheriv(ALGORITHM, keyBuffer, iv)
 return Buffer.concat([decryptor.update(dataBuffer.slice(96), 'utf8'), decryptor.final()])

My error happens in the last line of the decrypt function. I am storing the iv as part of the dataBuffer.

Thanks in advance!

I realized I had made a couple of mistakes with the original code that I posted, one of them as @TheGreatContini remarked was the size of the slicing which was being done in bits instead of bytes as it should be. Still, the biggest piece that I was missing was the authTag which always should be included in the decipher function setup.

Here is my working code for anybody interested for future references:

import crypto from 'crypto'
import logger from './logger'

const ALGORITHM = 'aes-256-gcm'

export const encrypt = (keyBuffer, dataBuffer, aadBuffer) => 
 // iv stands for "initialization vector"
 const iv = crypto.randomBytes(12)
 const cipher = crypto.createCipheriv(ALGORITHM, keyBuffer, iv)
 const encryptedBuffer = Buffer.concat([cipher.update(dataBuffer), cipher.final()])
 const authTag = cipher.getAuthTag()
 let bufferLength = Buffer.alloc(1)
 bufferLength.writeUInt8(iv.length, 0)
 return Buffer.concat([bufferLength, iv, authTag, encryptedBuffer])


export const decrypt = (keyBuffer, dataBuffer, aadBuffer) => 
 const ivSize = dataBuffer.readUInt8(0)
 const iv = dataBuffer.slice(1, ivSize + 1)
 // The authTag is by default 16 bytes in AES-GCM
 const authTag = dataBuffer.slice(ivSize + 1, ivSize + 17)
 const decipher = crypto.createDecipheriv(ALGORITHM, keyBuffer, iv)
 decipher.setAuthTag(authTag)
 return Buffer.concat([decipher.update(dataBuffer.slice(ivSize + 17)), decipher.final()])