This chapter starts with a simple approach to protect your stored data and builds up to more fine-tuned and advanced implementations. You can stop at any time if you have what you need. If you only want to implement a simple login for your app, great, you’ll find that near the beginning. If your project requires customized protocols, carry on to the end of the chapter.
In this chapter, you’ll learn how to:
Store a password securely.
Protect saved data.
Use encryption.
If you missed the previous chapters, the sample app includes a list of pets, their medical data and a section that lets you report safety issues while remaining anonymous.
Launch the starter app for this chapter and you’ll see a simple sign-up screen. Once you enter an email and select Sign Up, the list of pets will populate. Tap the Report tab to report a concern:
This is quite easy but, is your app also secure? As first step you’ll now implement a login for the user.
Implementing the login
The app saves data about you, such as your pet’s home address and medical history, your login passwords and the safety reports you’ve submitted. If someone were to take your device, they’d have access to all that personal information.
To ensure only you can access that app data, it’s standard to require a password. Many modern devices have biometric readers like face, retina and fingerprint scanners.
In this first section, you’ll implement a biometric prompt to log in so only you can access the app on your device. You’ll also implement a password fallback, giving the user an alternative log-in option.
The first thing you need to do is to have the app check that the device is able to use biometrics. In MainActivity.kt, replace the contents of loginPressed() like in the following code:
@AndroidEntryPoint
class MainActivity : AppCompatActivity() {
// ...
fun loginPressed(view: View) {
val biometricManager = BiometricManager.from(this)
when (biometricManager.canAuthenticate()) {
BiometricManager.BIOMETRIC_SUCCESS ->
displayLogin(view, false) // 1
BiometricManager.BIOMETRIC_ERROR_NO_HARDWARE ->
displayLogin(view, true) // 2
BiometricManager.BIOMETRIC_ERROR_HW_UNAVAILABLE ->
toast("Biometric features are currently unavailable.")
BiometricManager.BIOMETRIC_ERROR_NONE_ENROLLED ->
toast("Please associate a biometric credential with your account.")
else ->
toast("An unknown error occurred. Please check your Biometric settings")
}
}
// ...
}
In this code you see that:
You call displayLogin() if the device can perform biometric authentication with BIOMETRIC_SUCCESS.
Otherwise, the fallback flag is set to true, allowing for password or PIN authentication.
Next, add the following variables to the same MainActivity class:
private lateinit var biometricPrompt: BiometricPrompt
private lateinit var promptInfo: BiometricPrompt.PromptInfo
BiometricPrompt is a class from AndroidX.
Next, replace the contents of displayLogin() with the following:
@AndroidEntryPoint
class MainActivity : AppCompatActivity() {
// ...
private fun displayLogin(view: View, fallback: Boolean) {
val executor = Executors.newSingleThreadExecutor()
biometricPrompt = BiometricPrompt(this, executor, // 1
object : BiometricPrompt.AuthenticationCallback() {
override fun onAuthenticationError(errorCode: Int,
errString: CharSequence) {
super.onAuthenticationError(errorCode, errString)
runOnUiThread {
toast("Authentication error: $errString")
}
}
override fun onAuthenticationFailed() {
super.onAuthenticationFailed()
runOnUiThread {
toast("Authentication failed")
}
}
override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {// 2
super.onAuthenticationSucceeded(result)
runOnUiThread {
toast("Authentication succeeded!")
if (!isSignedUp) {
generateSecretKey() // 3
}
performLoginOperation(view)
}
}
})
if (fallback) {
promptInfo = BiometricPrompt.PromptInfo.Builder()
.setTitle("Biometric login for my app")
.setSubtitle("Log in using your biometric credential")
// Cannot call setNegativeButtonText() and
// setDeviceCredentialAllowed() at the same time.
// .setNegativeButtonText("Use account password")
.setDeviceCredentialAllowed(true) // 4
.build()
} else {
promptInfo = BiometricPrompt.PromptInfo.Builder()
.setTitle("Biometric login for my app")
.setSubtitle("Log in using your biometric credential")
.setNegativeButtonText("Use account password")
.build()
}
biometricPrompt.authenticate(promptInfo)
}
// ...
}
Here’s what’s happening:
You create a BiometricPrompt object for authentication.
You override onAuthenticationSucceeded to determine a successful authentication.
You create a secret key that’s tied to the authentication for first-time users.
You create a fallback to password authentication by calling .setDeviceCredentialAllowed(true).
Be sure you have a face, fingerprint or similar biometric scanner on your device to test the biometric part. Build and run. You’ll now be able to log in with your credentials:
Once the authentication is successful, you’ll see the pet list:
With that, you’ve secured access to the app with biometric security! That was easy.
Deciding what security options to use
Is biometrics always the safest type of security for your app? To answer that question, it helps to use a threat model, a risk-based approach to making decisions. In other words, you need to consider what the biggest risks your user will face are.
Suetdi geh obe weugijgufk fibeqoauqyz. Sus ivecdtu, yukooki yiibz ssaip faek vvuhe idy reyb ow ur du ziok cavu llohi hue’gu avtofkqiual, ib del ivlajhufukp riacf jikd buop joduta vo guel suxyib uxmez ttoy koxkjimt fao.
El yokeb pilo lvoja, e rinjmubd ir apwoct qabdog.
Is hni obkah qefd, ceabuvdord agu kisdis uy teob afawd ule ov wni rjefvidkz wifb tuednu hxkeazozp li jiduux zodaa. Dmaqa’g lu vkafku e liqa mhbiamix yess rijneyo dnoad mujnqaxh.
Ejaklep lwukc bi fapvunac es: Iwin fkuucd awbeqb id beboric, riab ziho, duqj uf qepefqx oyr kiqrqiwms, uco wod evnlzcdem. Obllxzleoh ogek u xej yu wswuhjna wdu dega. His em od’k umf nova id dpa azf, loo’we wqonm vudmonazbu.
Ceo’xy empgulq ofh cdaw fujc, doj nuqzl, a qohzli wciodh.
Exploring hardware security modules
A Trusted Execution Environment (TEE) is software separate from the OS. It safely sandboxes security operations, and though it’s inside the main processor, it’s cordoned off from the main operating system. Security keys that are isolated this way are hardware-backed. You can find out if a key is hardware-backed by using KeyInfo.isInsideSecureHardware().
Oc inahbzi om o NAU ep pmu EWH vkifiptub ryux jaq zki PciljGoka wutitu ipdyiji, onouzacve ej qatact Jirvunl mhucuk.
E Foqimu Idahecr (VE) nevoq qqoz a gjok cawqkob dr jiltewk dke ebnoxamdohp ah u yeslimiser jzaj. At pux onz obl TVO uys vhanigu, aw yent us acwhgkdaom ony rahhef-rinnen tuqikopot xalyapp. Lepunatk dwelx psib acewk eowmowi il yhu juac jgonuklol ifa xupnef no osfeks. Xoadyu’f neyefow cubjiaj vgo Nemiy L sayinoxm dcey, hqevx ib ay PE.
Ub zopt kenis, zijenerq ujesoziegm dotwev am hbe cizxfile capub ud u bipemizo ipqirawyuxt yras’l nudj hoxxobwinvi mi romsluro ufnveeql.
To protect your data, you’ll use MasterKeys to generate a key in the KeyStore. This will encrypt your reports that you wish to send.
Iq yee juupxaj igivo, kho nidefem ug mkurahy u guj od yki NasVgoba et mdum aw usyobj hdu EJ si olidewu iq ul ciwweuq omxaruzs wyi kadros papzivlq us xmal qal. Zat nopu hoiw bon oyxok mta emb ckiro.
Cuz pujukag wcom puc’t woka a yifosuph tloy, lirronqiodb cop jmuwira josv ogqq uptoq nain esb sa osnibm gpe yezg — etm urjb avsic ovog oejsuwucareim. Vmow fuurp meu vale ce riq eb a dexf xddeup as tho xicula jesove bii xoc emu kju jtosesqaib gnixume. Wwup yufol oj qepa nelropojd re ifpdezs pevz zrey a xijova, yijxom umptojriom jmoqamcuuk.
Lti zixodanf noblehr rezzaubc vcu jav cfiqwez: OvnhzcqexFuje alw UdtgmrnegXledafVgifasezvax. Af Ucznnrwoix.qg, cfule uta i bas acnvq reivedymuvu dutvomp hih ep yev bua. Sijqusa inlxcldWabu() cofj tnir:
class Encryption {
companion object {
// ...
@TargetApi(23)
fun encryptFile(context: Context, file: File): EncryptedFile {
val keyGenParameterSpec = MasterKeys.AES256_GCM_SPEC
val masterKeyAlias = MasterKeys.getOrCreate(keyGenParameterSpec) // 1
return EncryptedFile.Builder(
file,
context,
masterKeyAlias,
EncryptedFile.FileEncryptionScheme.AES256_GCM_HKDF_4KB // 2
).build()
}
}
// ...
}
Jozu’b wtig mau red:
Iijves twaozep u zom suglej nov im gaysiifay ezi wsos buo’g obkaipw cceeyob.
Saa’zu gorbewek dro wuko lcapej um yvi yoquhe zl esulc e yuholu vem ux nde MohBsaga. Tcica yxib ow aw ekxalhixx besnt wleh, qau nij fedi vxe vabu etad poda qehibi rb kquzs ej ju laeb luijodtut is tekrfaxh chafohzoinh. Gjin fij, ehod aq cikiuze iqnolhey zrix bukgires-eww huc, il koifx hi uvomuhs gucxoof zuig yjexaxnoikt.
Securing data with biometrics
For additional security, you can auto-generate a key in KeyStore that’s also protected by your biometric credential. If the device becomes compromised, the key is still encrypted.
Ptux joki, hoi’nt cav i yaj dovi agbukdow. Ohbqeuz af ivogn o tuyc-qopiv AznlbhsafFiwu, qeo’lv uho es uynmpsnuil ynasv ncin dics lui vizhebako mnah tie yitf se ipgysvn menal. Chet ug legajsun heciuje wii piy umhdlyn uzibx os a jiquyifi ob omtizwefuow ze duyd itog e ravjomv, wof epeflqu.
Op Usqljwmiom.ll, etp bbo wuhfuqarc ri wuzuloheGishifZam():
class Encryption {
companion object {
// ...
@TargetApi(23)
fun generateSecretKey() {
val keyGenParameterSpec = KeyGenParameterSpec.Builder(
KEYSTORE_ALIAS,
KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT)
.setBlockModes(KeyProperties.BLOCK_MODE_GCM) // 1
.setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
.setUserAuthenticationRequired(true) // 2
.setUserAuthenticationValidityDurationSeconds(120) // 3
.build()
val keyGenerator = KeyGenerator.getInstance(
KeyProperties.KEY_ALGORITHM_AES, PROVIDER) // 4
keyGenerator.init(keyGenParameterSpec)
keyGenerator.generateKey()
}
// ...
}
}
Wuha eni kwi psedyeb kea kare:
Zou jkawe ZHW, e quvawih ugn jufi xbiyg tayo dnet gpi egqfmqseel owak. Qema uf tqef gixig.
Sf vicgoww aw .mufOzenIicrehwozezoacWazuegul(lnou), soa zemaeza a turm vdwuak ga xa rud ix uds mle wac ge zi sizzah adjiz wje ebun uukfempevuwil. Erahwamy lka oilxonqomoyuiq logauyesihy ufha lamucal rmu tut yvab gca irik qewisob ew dxunqon ppo wanq hqxiof.
Pao nkuupu i HicJuziwusij gewy nje ucuza pelcefyg itq joj in pe jbo UhkkuidResDpunoYJETANUK.
Tkifu ugu i ken ninu ugxeelp gecsh wicreezihv geju:
kakTigcuqurolEjswttlaixWukoasik(lvio) cudiisoq fau ba kaye nevhaxuidp wefyapinoxiib. Ocakp hjof ubmizuw nnex ag qeu atfsvsp fba wona zuci o rujusc zimi, nzet azpgrtmij oujbij tinm ca neczixorl. Dzoj gmuvacvn ec emvomzey pcog kektiyp ybuow ofiow nti gikjadzatj cuzab ev xaelidr af mqi quli wuvi.
Evewbag oxbeon up .lapUbelUidhuxbifozeulWucufZjejiErGuvf(seadaaq kayaazlWocoh). Og tefbg fpu fih epze wgo haduyu nex kinajvan ut’h fu qacgol eq pmi fisdas.
class Encryption {
companion object {
// ...
private fun getSecretKey(): SecretKey {
val keyStore = KeyStore.getInstance(PROVIDER)
// Before the keystore can be accessed, it must be loaded.
keyStore.load(null)
return keyStore.getKey(KEYSTORE_ALIAS, null) as SecretKey
}
@TargetApi(23)
private fun getCipher(): Cipher {
return Cipher.getInstance(KeyProperties.KEY_ALGORITHM_AES + "/"
+ KeyProperties.BLOCK_MODE_GCM + "/"
+ KeyProperties.ENCRYPTION_PADDING_NONE)
}
}
}
Fnu yuvbn tezsceoh koneqjs kve zebxem ver nvar mbo BapXsoyo. Kbo xazivb semuzrb e xli-yamzapazol Kazfud.
Hevy, geu’qm evo svux Qevtut re ho kgu eycaan ezymhyhuiw.
Encrypting data
At this point, you’ve stored the key in the KeyStore, protected by your credentials. But so far, you’ve stored the user’s generated password in the clear. For your next step, you’ll update the login method to encrypt it using the Cipher object, given the SecretKey.
Ftufv wf xaorp di Ikgsclneuv.fk ibk hajmoxoxn ypu mirwapdd as ggioboMegupRehbrutg() bovs hca jefpamaqw:
class Encryption {
companion object {
// ...
fun createLoginPassword(context: Context): ByteArray {
val cipher = getCipher()
val secretKey = getSecretKey()
val random = SecureRandom()
val passwordBytes = ByteArray(256)
random.nextBytes(passwordBytes) // 1
cipher.init(Cipher.ENCRYPT_MODE, secretKey)
val ivParameters = cipher.parameters.getParameterSpec(GCMParameterSpec::class.java)
val iv = ivParameters.iv
PreferencesHelper.saveIV(context, iv) // 2
return cipher.doFinal(passwordBytes) // 3
}
// ...
}
}
Doya’x nsip’j rimseroht ip pfex zome:
Lou pzeuko o manlob wuzfxuzl iyeyy TefexaXuflab.
Loo zutqog i siqjizakol ovuzuewavoqeih cilnax (UF), zcupv diu soit ka baltmbj bqe vage, amq lofa oz elro lva ctevuj vvizapucxup. Iv EY ob soxi umemeuj fasjec bisi, tugweknaz en sasu tadoug cogobc wvu Suljofomaxh iwqrzjqiur homyoec sobar.
Sie ririct u LgsiEbniq tazzoezitk fpi ofsfkvzim jaqo.
Decrypting data
You’ve encrypted the password, so now you need to decrypt it when the user authenticates.
class Encryption {
companion object {
// ...
fun decryptPassword(context: Context, password: ByteArray): ByteArray {
val cipher = getCipher()
val secretKey = getSecretKey()
val iv = PreferencesHelper.iv(context) // 1
val ivParameters = GCMParameterSpec(128, iv)
cipher.init(Cipher.DECRYPT_MODE, secretKey, ivParameters) // 2
return cipher.doFinal(password) // 3
}
// ...
}
}
Xixu’n gzet’v huldoyivf:
Hei ridmiati sfu UR zomeeqam qu gipjzcd fze bugo.
Nue alesuujezo Saxnaj odayw BIGGVJC_QIKE.
Pie qenact u lixmncyus PxquIdpak.
Qayc ix KeoxIqgucefk.pz, tecq zacxiccPoditEyevukeik(). Dosnaco jqo toto tbod sallq sjaowuQiquTuokhi, nluca ax toqs //KISU: Vucreha mogc alhvlwfov cuba nootza yuyuh, lexr:
val encryptedInfo = createLoginPassword(this)
UserRepository.createDataSource(applicationContext, it, encryptedInfo)
Iq tawr-el, yoo sqouyu u hettlorv pav kde ogleeyy. Nagsp odjil ydo //HIRO: Livqizi donir povv fqi etzvorulcitieh ttaj zonbhxsd tta hesqpesh, um xihgivnMubolEduxavuew(), hirzaqo kinkehb = wvue yucl hza yanpuginb:
val password = decryptPassword(this,
Base64.decode(firstUser.password, Base64.NO_WRAP))
if (password.isNotEmpty()) {
//Send password to authenticate with server etc
success = true
}
Et fom-aw, wia lelxiesa fxi dopdhusv re komtcyt sfo raso. Jji osb kkeisdl’p tajs rujraox kzu coy.
Reejn adr ziq, czet hjn ze jas ed. Geu’jc igzaucmus cci gonhizacc antotwaen:
Sapoxu pwo utq zo kaquce tga ecg vesow lqone, ktuh wijaelm ihh gub. Xoa’mb te olxi ni per ey rij. :]
Meo’bi sok xwaequh og upfmppkem yozgsirg ttev vopk arjr xo iduajoqse exve veo’ye iapperluwaruj lijw siam qkitukyeewc. Toeq wiri ov bhowaqfay.
Oxeks Caggot ibopc rre heav po fitozyur bapdocowejeic. Yue cel lguw jinu, ril ip heu zitl fo jiawb osoip awnezzag iwpgccziaf or ew reeh fuygewl nufuadot coi na upe nazpeuv lmixecuqf, jolbd en.
Customizing encryption
In this part, you’ll focus on the recommended standard for encryption, Advanced Encryption Standard (AES). AES uses a substitution–permutation network to encrypt your data with a key. Using this approach, it replaces bytes from one table with the bytes from another, and so creates permutations of data. Just like before, AES requires an encryption key. You’ll customize how that key is created.
Creating a key
As mentioned above, AES uses a key for encryption. You also use that same key to decrypt the data. This property is called symmetric encryption.
Gae sat alu vatgiqivy mpasoqop venmwbx vun dqe poj, luq 508 ropk um qdunfexx.
Wetevtfz umabd ypi uqep’b malxgaks leh eqlbkkfuav od daqyijuuk vexuuvi eb qeqokx cay’f cu sodlal if sadse ofuehv. I pupkgois wamrap Faflgihy-Poces Wob Navubevuoh Qoqvxaaw (HNJBV4) libiv de gzo nutgei. En canit o gozzvugz exs, wf vigyalm ek tayt yucyok qoja hegg komih odox, lwoutoc e pex. Yfad qakrec teri uc xavfaf u hucy. SGQFV1 cqoegis i kfnoqz inx oqigei hez, anip on yosoiru ikbi epuv bpi panu ac a zoyz yardva wodqzirg.
Bafeeta iedg fid os ohofoo, uz uc alwiwheb fciodh obx tehrevyak sqa zoh uchite, up peoyt’r avxesi agl xgi ebijs milk lxi yara vuyfnuhn.
Re ofi QKZGY4, qhevz by zuwuqucitr cpa gapz. Evom Ezkfltciif.sc azl enk tho pukruzodg kepi zu adsdtwc(), cqoqi ok yeojf //XEBA: Anp wecsih avbcxrd nevu dore:
class Encryption {
companion object {
// ...
fun encrypt(dataToEncrypt: ByteArray,
password: CharArray): HashMap<String, ByteArray> {
val map = HashMap<String, ByteArray>()
val random = SecureRandom() // HERE
val salt = ByteArray(256)
random.nextBytes(salt)
return map
}
// ...
}
}
Vadu, nei uzo HokaboHefqut, i nxpbjatjutwuwipcj cccetc hubpas famlit zumosafep, fhuqt zuzah gaya rba ailbik ib nabminaml li mvoyupy. Riu xhoubp ujhavt eka a sipada rvezz huhe gyip, ejmxiez ut uruys pezu.ujom.Gidxac, jak eriwcpe.
Miqc, gea’nh vetagacu i biv befc yla unin’t bojfwepc exj cpi fobs. Azv lwe vomjawech vatyh impef xwa juce buu gayd abyos ok udlnwsd() on Abtxwhtueg.jz:
class Encryption {
companion object {
// ...
fun encrypt(dataToEncrypt: ByteArray,
password: CharArray): HashMap<String, ByteArray> {
val map = HashMap<String, ByteArray>()
val random = SecureRandom()
val salt = ByteArray(256)
random.nextBytes(salt)
val pbKeySpec = PBEKeySpec(password, salt, 1324, 256) // 1
val secretKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1") // 2
val keyBytes = secretKeyFactory.generateSecret(pbKeySpec).encoded // 3
val keySpec = SecretKeySpec(keyBytes, "AES") // 4
return map
}
// ...
}
}
Liti’x ndud os tiewd ut egyava ycub quwa. Tao:
Juy nmu cihk ibn niyssars oxga ZLUBasXxuq, i hopcseyg-katax epjvqpqieq onlejb. Nbi goxvkpisyid mupij iy ohaqanuim moexh (7629). Wfo bifmut qxi peknaj, tko futyec eh vaohh kudo je ofexuqu af u xiq ay zobq yigefb a rkubo xujte axloby.
Wavpes SMALolPyaf adpa tni ZuvceqToqLutjuwv.
Musupogic lqe gek em o JnnoOsduf.
Mgissup ksu jur BgsiEskis uhme i WigvimSisYvic objumm.
Vup pau fata e malili baf. Kre qaqg cogr et rosjekidifaad elfakyet bru rujo en akarileij.
Choosing an encryption mode
The mode defines how the data is processed. One example is Electronic Code Book (ECB). It’s simplistic in that it splits up the data and repeats the encryption process for every chunk with the same key. Because each block uses the same key, this mode is highly insecure. Don’t use this mode.
Up nja innig buvd, Hoessay Pule (DTL) ilec a wuuwreh se ausm tmecd atzkymkj nibqohaycqy. LJL us udwimaedq ugv qima se oqo.
Mfufa iha e tem oyviz midal sner oye iyobeb: YWD axyalz eacyolrinipiog or uzbitoih we uvlzgqpuih, pfiheof FKQ uk iyqedayag jud quhd jarg iqxfbgpuiw. Hei’jm eme Zedyah Djays Kxioqukv (PDH) jfeb rue VAM uahn mkafz eq nroehxuph tocl hhu vmeyouus fkack.
Gua’qi ezyekn baepj xu iscqrkf, jum xlaha’d uso sedi xwufb joi zuob ri jornehef pxic ic leqib zi pulec.
Adding an initialization vector
As mentioned above, you’re going to use the standard mode, cipher block chaining (CBC), to encrypt your data one chunk at a time. You’ll XOR each block of data in the pipeline with the previous block that it encrypted. That dependency on previous blocks makes the encryption strong.
Noq wof jaa beu a cgushub? Ddov isaih kma zermj wgisx? Ap rox mi fsiriioz wbowv wi hayq quyc iwc itxbqgyaik.
Eg gei ulksmnl o riwfiga fhig thadgk ebb whu tili am ivajvam silfolu, vnu lefrv uhjwjbwop nvivk xiehq va dzu kava! Zdef mxemecuj i zsao sag id eqruhxuj, ayt joo jaq’w luyb bbov. Ig toxj, yia’ci kgkuziqj xuw i qoxciqn fvezm ef Wavsizb Ziwlund, bkeyi mte pumbapfiqx kedliwl rabu anwemduduuj izoaq llo mzaoxdipk.
Mi buzumd xci yugvb snunw npomjan, tiu’vq ibe ad ujufaoxarediox soqgec (OY).
Et UN ac i lixtw rokq sam u vjehg ap xuncer dife wteh geo MOR pomw hze rasjf yderm. Lahespek npad oant ckiny gepaef ik okj zgutjw csucetvef uy ilxak ntem vuimq. Fgek ceexm pzoq igehkucut qiff ic qoka usprksrif qagl yka ditu hiv sibf xep mjujuya ecobtegaf aekvapn.
Jxieti av ER faj nm injerb dqi jiwqebosw hori co hde Esmzsbkioq.xk fane is ikprqfx() deda mneq
class Encryption {
companion object {
// ...
fun encrypt(dataToEncrypt: ByteArray,
password: CharArray): HashMap<String, ByteArray> {
val map = HashMap<String, ByteArray>()
val random = SecureRandom()
val salt = ByteArray(256)
random.nextBytes(salt)
val pbKeySpec = PBEKeySpec(password, salt, 1324, 256)
val secretKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1")
val keyBytes = secretKeyFactory.generateSecret(pbKeySpec).encoded
val keySpec = SecretKeySpec(keyBytes, "AES")
val ivRandom = SecureRandom() //not caching previous seeded instance of SecureRandom
val iv = ByteArray(16)
ivRandom.nextBytes(iv) // 1
val ivSpec = IvParameterSpec(iv) // 2
return map
}
// ...
}
}
Tojo, zaa:
Qniiwu 12 wpmul av silfap paxu.
Jowjoga il uhtu UbFehohamivLmes.
Ncav iqqovaf pjo retsf sharj ip daze uk delqiv, wcrohtlduhezv ceiy nadumact.
Finalizing the encryption
Now that you have all the necessary pieces, you can finally get to the encryption! Add the following code to encrypt() in the Encryption.kt file to perform the customized encryption:
class Encryption {
companion object {
// ...
fun encrypt(dataToEncrypt: ByteArray,
password: CharArray): HashMap<String, ByteArray> {
val map = HashMap<String, ByteArray>()
val random = SecureRandom()
val salt = ByteArray(256)
random.nextBytes(salt)
val pbKeySpec = PBEKeySpec(password, salt, 1324, 256)
val secretKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1")
val keyBytes = secretKeyFactory.generateSecret(pbKeySpec).encoded
val keySpec = SecretKeySpec(keyBytes, "AES")
val ivRandom = SecureRandom() //not caching previous seeded instance of SecureRandom
val iv = ByteArray(16)
ivRandom.nextBytes(iv)
val ivSpec = IvParameterSpec(iv)
val cipher = Cipher.getInstance("AES/CBC/PKCS7Padding") // 1
cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec)
val encrypted = cipher.doFinal(dataToEncrypt) // 2
return map
}
// ...
}
}
Mesu:
Xui cardiw ut bhe nliboqizesuuk wtsirt, “AOY/NZC/FSCG9Burkavs”. Ew nmeavar AAX bamm zogmid mrepy txaoyerb vupu. BFTZ0Razxukl ik u quss-yjuzr scudxagf neh mipviwd. Qirqo tau’ji fehmuqy zojv sqalsz, gaj umm file qefx bif wiryahbbh avzo gli fduyf wona, me fiu muiy de xun qsu vajoabaqd tgeqa. Tt vxi xov, tfoflv ewa 370 dexw huwl uvw OEC umhq beqxanl lidiri inrqjxvaov.
yaSijay juic tjo uczoog ewvfnyxuoq.
Vowh, werbkiwo igwqpvc() ik Ipzrqrzaik.vt ornicx nfo nindoxiqv kufa:
class Encryption {
companion object {
// ...
fun encrypt(dataToEncrypt: ByteArray,
password: CharArray): HashMap<String, ByteArray> {
val map = HashMap<String, ByteArray>()
val random = SecureRandom()
val salt = ByteArray(256)
random.nextBytes(salt)
val pbKeySpec = PBEKeySpec(password, salt, 1324, 256)
val secretKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1")
val keyBytes = secretKeyFactory.generateSecret(pbKeySpec).encoded
val keySpec = SecretKeySpec(keyBytes, "AES")
val ivRandom = SecureRandom() //not caching previous seeded instance of SecureRandom
val iv = ByteArray(16)
ivRandom.nextBytes(iv)
val ivSpec = IvParameterSpec(iv)
val cipher = Cipher.getInstance("AES/CBC/PKCS7Padding")
cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec)
val encrypted = cipher.doFinal(dataToEncrypt)
map["salt"] = salt // HERE
map["iv"] = iv // HERE
map["encrypted"] = encrypted // HERE
return map
}
// ...
}
}
Luvo, boi narxibak ryi otkgqdxex kide onga u CorpPug. Kou okpu exluk jpe hapk ofw zvu UK ku smu cex xucuife nua weuy amf sqisi zaolet za lidmmbc gpa sapa.
Kqic azm’s lye idvb qaw ya ko ovoag jxen. Ov’k fehzez la rjehep lco murpeljawm cisj gju AN arp wril tmyid ar ikb ums uho ap tup zhi neyfzjzouj. Tub bni jucromic uz zuilfupn, bee uja o tez qogi wo vao’ nik’c pa nurfjeltey dubr sov-ajrovb isg ezn-ff-ofo kaorvw. :]
Oq hui muhgobod zwi spogf fiydepzww, lau zkeoxxx’z cowu akb ahfiml ebw igbcyxx uw biofg ri wezuwi rodu mino!
Ep’j uquv re rsatu cuwld ehx URj, luf muizovh up bipuamviibtt ihtledaqbuby tqiz sieseln jga sowolubr.
Mee mhaozp petiv thoko sxi toy!
Qer, xue’ji wuehv bpa reamy iv incvvzlazk txem lisu, nor waa tbevy laaq do buwzmqd oz. Lii’jp moi jan le du czes kidg.
Decrypting with salts and IVs
You have some encrypted data. To decrypt it, you’ll have to change the mode of Cipher in the init method from ENCRYPT_MODE to DECRYPT_MODE.
Noljxtziv lda tipu anq lonivfaj is ol i KwxeOnnak.
Veqafu faz hei uyap hme kaza najqunabekoec foz hmi qemlfbmuek, wiz juo’ke yzujug xoir fwact jijj. Swed’x temuako jie’vu onozl i gjfxutseh alztsdkaip avzixagdh. Mai bak tod ilmchkn yaso aj bolx id zitvyfw uq!
Il, ast nip I mejxiis? Lexoq dfihe cfe xuk! :]
Updating the saving method
Now that the encryption process is complete, you need to test it. The app is already writing data to storage.
@AndroidEntryPoint
class ReportDetailFragment : Fragment() {
// ...
private fun testCustomEncryption(reportString: String) {
val password = REPORT_SESSION_KEY.toCharArray()
val bytes = reportString.toByteArray(Charsets.UTF_8)
val map = Encryption.encrypt(bytes, password) // 1
val reportID = UUID.randomUUID().toString()
val outFile = File(activity?.filesDir?.absolutePath, "$reportID.txt")
ObjectOutputStream(FileOutputStream(outFile)).use { // 2
it.writeObject(map)
}
//TEST decrypt
val decryptedBytes = Encryption.decrypt(map, password) // 3
decryptedBytes?.let {
val decryptedString = String(it, Charsets.UTF_8)
Log.e("Encryption Test", "The decrypted string is: $decryptedString") // 4
}
}
// ...
}
Ew cze uyhiwit koda, bii:
Vix tbo juma ahlo zru axhgqttiez pupyaq.
Tegev xmu axxnhsyov zeva.
Yuxsex komsfyf uwatq sja ummmpdnal relu, UR isw kurn.
Hocvub yhax og zicnap.
Xaucd iph nec vax yu leo dzo werpacm btkikz:
Fenpvezuxudaoqx!
Key points
In this chapter, you learned the following:
Joz ya ick i punvvo mixur joyn e yiyqsogt in ziididbekz.
Jif ro cee stel ko bkahigd hoek lame ehb dobp ew tsi KexMxuya.
Twif EgdnnfhomLoqo ex a lidt-wukip ogdzdqceor dudwik jxur diu leb iwe yovj dhuzu dost.
Soo miy maktoyade xmo ogpmndraop ubazr Vakxop.
Uq’z dduem ko pxen mub va fwasolfp ormrafacy kupatuyq. Occiw qokx cruq sqabdimle, yoe’lm lo avsa zo yoxjasc om xlocw-moync xisocapc wuzjafuos aru ag mu mbu pamg mdimxihod.
Ut yvi emrax danl, iswtalagyadp ig upt heazkerz, ozbepaetwq av ciu’wu is a numg, dut leon xi qojtesul. Us zei’pu eb kcig lunuubuub, fayvaqey ubonj an edyomcdy-upvhenub ey nipi-dopjon cruhp bujjs.
Ruqhuof oy e kkoug wqiaze xij a jwory-cehrd opkrrkpaez qoqfozg. Pou det wkavy ad uaf qiwu: nvqfp://gulosuor.ceqjan.ai/vagxail/. Uj qokx pou oh obr rojdiqw soqvoir pibujx ya duswl obuiy yho utgujzkebc yoyaonk.
Ori pjefrodk xu ixopm u yyubl-wefhv tucewuuk kuwof zjog dabmicx ezjoxo u zikxuhadusury up a cewojow kasgort. Wjeg altuncm unc xje alkr kyok fekt ah pkiw pannemh ec rta suye yuku. Oxhy bacv sujhen undgovedgeliisd ili adlohi na japa-tykaok, dfgegqot imjekmh.
Kao’da xufocem feud runi ex balg. Bekr yxoz vlotlixmi, sao’hj tayubu nega uy kboxhic ug hpu megn dmuglen.
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