crypto, certificaten, ssl, pki what can possibly go wrong? · issuer: c=gb, st=greater manchester,...
TRANSCRIPT
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Crypto, Certificaten, SSL, PKI What can possibly go wrong?
ISC2 cryptonight
10 juni 2014
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Introductie
Arthur Donkers & Ralph Moonen
Partners bij ITSX
IANAC
10 juni 2014 ISC2 cryptonight 2
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Agenda
Symmetrische en asymmetrische crypto
Certificaten
SSL en TLS
Oeps…
10 juni 2014 ISC2 cryptonight 3
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Vragen?
Ja graag !!!
ISC2 cryptonight 10 juni 2014 4
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Cryptografie en cryptanalyse
Cryptografie is geheimschrijverij
Cryptanalyse is systematische analyse van versleutelde
berichten
10 juni 2014 ISC2 cryptonight 5
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Symmetrische crypto
One key to rule them all… Zelfde sleutel voor encryptie en decryptie Combinatie van bitshuffling en XOR (short version)
10 juni 2014 ISC2 cryptonight 6
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Voorbeelden
DES, 3DES, AES (block ciphers): opereert op blokken van (meestal) 64 bits, 128 bits etc)
10 juni 2014 ISC2 cryptonight 7
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DES (single run, 56 bit)
10 juni 2014 ISC2 cryptonight 8
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AES, replaces DES
10 juni 2014 ISC2 cryptonight 9
Substitute, permutate network
inpu
t
⨁
S1
S2
S3
S8
⋯
outp
ut
subs. layer
perm. layer inversion
k1
⨁
S1
S2
S3
S8
⋯
k2 S1
S2
S3
S8
⋯
⨁
⋯
kn
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Stream ciphers
PRNG levert pseudo random getallen stroom: XOR met bericht.
10 juni 2014 ISC2 cryptonight 10
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Stream ciphers, native
10 juni 2014 ISC2 cryptonight 11
Voorbeeld: RC4 HTTPS en WEP
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Stream ciphers, block based
10 juni 2014 ISC2 cryptonight 12
Je kan een block cipher omzetten in een stream cipher
Padding
Feedback loop
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Electronic codebook (ECB)
10 juni 2014 ISC2 cryptonight 13
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ECB, same input, same output
10 juni 2014 ISC2 cryptonight 14
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Cipher block chaining
10 juni 2014 ISC2 cryptonight 15
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CBC decryption
10 juni 2014 ISC2 cryptonight 16
Watch out: manipulating IV leads to control of plaintext!
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CBC, padding oracle
10 juni 2014 ISC2 cryptonight 17
D(k,⋅) D(k,⋅)
m[0] m[1]
⊕ ⊕
c[0] c[1] IV
Since messages must be a multiple of the block size, padding necessary. Every byte of the padding is the length of the padding. i.e.: 0x0505050505 or 0x030303.
let g be a guess for the last byte of m[1]
⨁ g ⨁ 0x01
= last-byte ⨁ g ⨁ 0x01
if last-byte = g: valid pad otherwise: invalid pad
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Asymmetrische crypto
Twee sleutels, één privé en één publiek
10 juni 2014 ISC2 cryptonight 18
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Asymmetrische crypto
Bijna altijd gebaseerd op moeilijk omkeerbare wiskundige problemen:
Factoring (priem getallen)
Discrete logarithmen
10 juni 2014 ISC2 cryptonight 19
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RSA (factoring)
10 juni 2014 ISC2 cryptonight 20
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Elliptic Curve
10 juni 2014 ISC2 cryptonight 21
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Asymmetrische crypto
10 juni 2014 ISC2 cryptonight 22
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Asymmetrische crypto
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Authenticatie
Digitale handtekeningen
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Certificaten
10 juni 2014 ISC2 cryptonight 24
Trust model (wij van wc eend…)
Afspraak is dat we een aantal CA’s vertrouwen
Hoeveel is genoeg?
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Certificaten
10 juni 2014 ISC2 cryptonight 25
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Certificaten
10 juni 2014 ISC2 cryptonight 26
X509.v3 standaard
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Certificaten
10 juni 2014 ISC2 cryptonight 27
X509.v3 certificaat bevat Object ID’s in ASN.1 codering.
Geheel is ondertekend door een CA die iedereen vertrouwd.
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Certificaten
10 juni 2014 ISC2 cryptonight 28
Version: 3 (0x2) Serial Number: c3:e0:e7:bf:11:37:a3:00:20:64:53:a1:21:53:4e Signature Algorithm: sha1WithRSAEncryption Issuer: C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO SSL CA Validity Not Before: Dec 11 00:00:00 2013 GMT Not After : Dec 10 23:59:59 2018 GMT Subject: OU=Domain Control Validated, OU=COMODO SSL, CN=office.itsx.com Subject Public Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: (2048 bit) Modulus (2048 bit): <hex data> Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Authority Key Identifier: keyid:1B:6B:BD:1F:8A:49:18:94:54:37:55:B4:20:17:ED:37:B9:77:18:7D X509v3 Subject Key Identifier: 0C:95:31:B1:2B:04:EE:45:1C:B7:EA:AE:28:E4:C2:20:E4:B0:1E:09 X509v3 Key Usage: critical Digital Signature, Key Encipherment X509v3 Basic Constraints: critical CA:FALSE X509v3 Extended Key Usage: TLS Web Server Authentication, TLS Web Client Authentication X509v3 Certificate Policies: Policy: 1.3.6.1.4.1.6449.1.2.2.7 CPS: https://secure.comodo.com/CPS Policy: 2.23.140.1.2.1 X509v3 CRL Distribution Points: URI:http://crl.comodoca.com/COMODOSSLCA.crl Authority Information Access: CA Issuers - URI:http://crt.comodoca.com/COMODOSSLCA.crt OCSP - URI:http://ocsp.comodoca.com X509v3 Subject Alternative Name: DNS:office.itsx.com, DNS:www.office.itsx.com
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Software
10 juni 2014 ISC2 cryptonight 29
Secure Socket Layer (SSL)
SSLv2
SSLv3
Transport Layer Security (TLS)
TLS 1.0, 1.1, 1.2 (en 1.3)
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Software
10 juni 2014 ISC2 cryptonight 30
TLS is opvolger van SSL
TLS kent sterkere algorithmen
TLS 1.0 en SSLv3 zijn niet compatibel
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Attacks, wiskunde
10 juni 2014 ISC2 cryptonight 31
Public key systemen zijn niet mathematisch bewezen veilig…
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Attacks, algoritmen
10 juni 2014 ISC2 cryptonight 32
RC4, geen homogene uitvoer (lichte voorkeur voor waarden) in 1e 256 bytes
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Attacks, algoritmen
10 juni 2014 ISC2 cryptonight 33
Dual EC DRBG random number generator is backdoored (NSA)?
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Attacks, protocol
10 juni 2014 ISC2 cryptonight 34
Renegotiation aanvallen Injecteren van plain tekst
Man in the Middle
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Attacks, renegotiation
10 juni 2014 ISC2 cryptonight 35
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Attacks, protocol
10 juni 2014 ISC2 cryptonight 36
BEAST attack misbruik van CBC, door voorspelbare IV wordt CBC EBC
is gericht tegen de browser
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Attacks, BEAST
10 juni 2014 ISC2 cryptonight 37
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Attacks, protocol
10 juni 2014 ISC2 cryptonight 38
CRIME/TIME/BREACH attack Compression side channel
Verschillende data geeft verschillende compressie resultaten
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Attacks, protocol
10 juni 2014 ISC2 cryptonight 39
Padding Oracle attack Misbruik de padding om bytes te ontsleutelen
Hangt af van timing en foutmeldingen
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Attacks, implementatie
10 juni 2014 ISC2 cryptonight 40
Te veel om op te noemen…
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Attacks, implementatie
10 juni 2014 ISC2 cryptonight 41
Slechte random number generators:
Genereert identieke sleutels…
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GCD
Indien twee RSA keys een deler gemeen hebben (omdat slechte random generator werd gebruikt) dan is dat met Euclidius’ algoritme (2300 jaar oud) zeer snel te vinden.
10 juni 2014 ISC2 cryptonight 42
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Advies
10 juni 2014 ISC2 cryptonight 43
• Cryptografie is moeilijk
• Goede cryptografie is bijna onmogelijk!
• Gebruik beschikbare implementaties, zelf implementeren is moeilijk!
• Laat alle crypto protocollen reviewen
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Advies
10 juni 2014 ISC2 cryptonight 44
Don’t even think of ‘inventing’ your own algorithm or protocol!
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Tenslotte…
10 juni 2014 ISC2 cryptonight 45