( ) C05-101
1
kryptos ( ) graphein ( ) " " -------------- ABCDE abcdef 123456 (Encrypt) ------------- #@%$/\ [~^%$)<> (Decipher) -------------- ABCDE abcdef 123456
(1/2) (Plaintext) (Ciphertext)
(2/2) (Encryption Algorithm) (Decryption Algorithm) (Decipher) (Cryptanalysis)
(Why Cryptography) (Confidentiality) (Authentication) (Integrity) (Non-repudiation )
(Privacy) (Authenticity) (Message) (Sender) (Integrity) (Non-repudiation) (Authentication)
Kerckhoff Principle
(Key) (bit)
(Computationally Secure)
(1/2) (Ciphertext Only Attack) (Known Plaintext Attack) (Chosen Plaintext Attack) ( )
(2/2) (Chosen Ciphertext Attack) ( ) (Brute-Force Attack)
2
(substitution) (transposition) (product) (secret-key) (HASH) (block cipher) (stream cipher)
(substitution) (transposition) (Product)
(secret-key) (HASH)
vs. (block cipher) n (M M1 M2 Mn ) E(M,K)=E(M1,K)E(M2,K)..E(Mn,K) (stream cipher) (keystream) plain text XOR cipher text
Caesar 50 Julius Caesar ATTACK AT DAWN DWWDFN DW GCZQ Caesar C=E(P) = (P+k) mod (26) Caesar P=D(C) = (C-k) mod (26)
2 vs.
Data (Symmetric Encryption, Secret Key Encryption, conventional Encryption) Data
(Confidential)
Data (Asymmetric Encryption Public Key Encryption) - (public key and a private key) Data Data Data
vs. key key N, key N email
Secret Public Private
3
Data Encryption Standard (DES) Triple DES (3DES) IDEA Blowfish Twofish RC4 RC5 RC6 AES (Advanced Encryption Standard) Rijndael
DES DES 1977 (NIST) (Confusion) (Diffusion) DES 56 64 16 56 DES
Triple DES 1992 DES Triple DES ( 48 ) 3DES K1 K3 K2 168 DES-EEE3 DES-EDE3 DES-EEE2 DES-EDE2 3DES PGP S/MIME
3DES DES-EDE3 K1 DES K2 DES K3 DES K3 DES K2 DES K1 DES
(1/2) (AES Advanced Encryption Standard) NIST DES 1997 4 AES (sensitive) (unclassified) 2000 10 NIST (Belgium) Joan Daemen Vincent Rijmen Rijndael
(2/2) Rijdael AES 128 128 192 256
DES 3DES AES 64 64 128 56 168 128/192/256 16 48 10/12/14 ( )
Deffie-Hellman Key Exchange DH RSA 1978 Rives Shamir Adleman (Elliptic Curve ECC ) ECC RSA
(1/2) (Hash Function) (1/2) (Hash Value) (Message Digest)
(2/2) (Hash Function) (2/2) (One way transformation) (collision resistance) (Digital Fingerprint) (Diffusion)
(Hash Algorithms) MD2 MD4 MD5 Secure Hash Algorithm (SHA) RIPEMD-160
Message Digest 5 (MD5) 1991 Ron Rivest MD5 MD4 MD4 MD5 512 16 32 512 128 UNIX/Linux shadow
SHA SHA-1 (Secure Hash Algorithm ) (NIST) (DSS) 2 64 512 SHA 160 MD5 ( 32 ) SHA-1 SHA PGP
RIPEMD-160 RACE 512 160
MD5 128 512 SHA-1 160 512 RIPEMD-160 160 512 64 80 160 (4 16(4 20(2 5 16 ) ) ) 8 2 64-1 * 32.4Mbps 14.4Mbps 13.6Mbps * Pentium 266MHz (http://www.eskimo.com/~weidai/benchmarks.txt)
4
PKI PKI PKI PKI PKI
PKI PKI PKI
11 Data 8A48 (public Key) 3A78 Data (Private Key)
~*~*~*~ ~*~*~*~ ~*~*~*~
MD5 SHA RSA
MD5 SHA RSA
(Digital Envelope)
PKI (vs. ) (confidentiality) (integrity) (Code Signature)
(Certification Authority) (Trusted Third Parity) CA ( verisign Thawte Consulting)
(Certificates) CA Serial Number ( ) Subject ITU-T X.509 version Issuer Public Key Validity Period Extensions CA Signature (issuer).
X.509 X.509 ASN.1 (Abstract Syntax Notation 1) ASN.1 DER (Distinguished Encoding Rules) BASE64
Base64 ASCII -----BEGIN CERTIFICATE----- MIICWDCCAgICAQAwDQYJKoZIhvcNAQEEBQAwgbYxCzAJBgNVBAYTAlpBMRUw EwYDVQQIEwxXZXN0ZXJuIENhcGUxEjAQBgNVBAcTCUNhcGUgVG93bjEdMBsGA 1UEChMUVGhhd3RlIENvbnN1bHRpbmcgY2MxHzAdBgNVBAsTFkNlcnRpZmljYXRp b24gu2vydmljzxmxfzavbgnvbamtdnd3dy50agf3dguuy29tmsmwiqyjkozihvc NAQkBFhR3ZWJtYXN0ZXJAdGhhd3RlLmNvbTAeFw05NjExMTQxNzE1MjVaFw05Nj EyMTQxNzE1MjVaMIG2MQswCQYDVQQGEwJaQTEVMBMGA1UECBMMV2VzdGV ybibdyxblmriweayd VQQHEwlDYXBlIFRvd24xHTAbBgNVBAoTFFRoYXd0ZSBDb25zdWx0aW5nIGNjMR 8wHQYDVQQLExZDZXJ0aWZpY2F0aW9uIFNlcnZpY2VzMRcwFQYDVQQDEw53d3 cudghhd3rllmnvbtejmcegcsqgsib3dqejaryud2vibwfzdgvyqhroyxd0zs5j b20wxdanbgkqhkig9w0baqefaanladbiakeampil7ar3aspuuwurhzpvmrsm3gp I2PzIwMh39l1h/RszI0/0qC2WRMlfwm5FapohoyjTJ6ZyGUUenICllKyKZwIDAQABMA0 GCSqGSIb3DQEBBAUAA0EAfI57WLkOKEyQqyCDYZ6reCukVDmAe7nZSbOyKv6K UvTCiQ5ce5L4y3c/ViKdlou5BcQYAbxA7rwO/vz4m51w4w== -----END CERTIFICATE-----
3 1 2 (Certificate Authority) 4 (Registration Authority) 1 Repository 2 3 4
(GPKI) (GPKI) (Government Public Key Infrastructure, GPKI) GPKI GRCA http://grca.nat.gov.tw GPKI GPKI
PKI PKI PKI
5
SET, S/MIME, PGP.. SSL, SSH IPSec
SSL(Secure Sockets Layer ) 1994 netscape TCP SSL HTTP+SSL=HTTPS SSL (Authentication) RSA DSS X.509 (Confidentiality) IDEA 3DES RC4 (Integrity) MD5 SHA (MAC) SSL
SSL SSL SSL TCP SSL SSL (HTTP LDAP SMTP.) SSL SSL SSL. SSL TCP IP
SSL Client_hello Server_hello Certificate Server_key_exchange Certificate_request Server_hello_done Certificate Client_key_exchange Certificate_verify RSA hello message RSA Change_cipher_spec Finish Change_cipher_spec Finish
TLS (Transport Layer Security) SSL 1999 IETFTLS 1.0 (RFC2246) TLS SSL TLSSSL v3.1 TLS TCP Telnet FTP HTTP
Secure Shell (SSH) SSH SSH v1 v2 SSHv1 telnet rlogin rsh rexec SSHv2 SSHv1
SSH ssh ssh <host> <command> ssh X11 DISPLAY Port Forwarding ssh ssh (3) X11 Forwarding Vnchost:5900 Localhost :5900 Text Port 22 ssh vncviewer vnchost (5) Port Forwarding ssh -L 5900:localhost :5900 <vnchost>
SSH Diffie Hellman RSA SSH IDEA Blowfish AES 3DES RSA DSA PKI telnet rcp rsh rlogin ftp ssh sftp scp
IPSec IPSec IETF(Internet Engineering TaskForce) Ipv6 IPSec (confidentiality integrity authentication key management) IPSec OSI IP
IPSec (IETF) IPv4 IPv6 IPSec IPSec (transport mode) (Tunneling mode)
IPsec (1/3) IPSEC IKE AH ESP IPSEC DOI
IPSec (2/3) IPSec (IKE) (SA) AH(Authentication Header ) IP IP IP :
IPSec (3/3) ESP(Encapsulating Security Payload ) IPSec AH ESP
IPSec Transport Mode Host B Internet Host A IPSec between Hosts IP (IP Header) AH or (IP Payload) ESP
IPSec Tunnel Mode Host A IPSec X IPSec Y Host B 1 IPSec between Gateways 2 IP (IP Header) (IP Payload) IP (IP Header) (IP Payload) IP AH ESP IP ESP (IP Header) (IP Payload) Trailer ESP
S/MIME PGP
S/MIME MIME S/MIME (Secure/Multipurpose Internet Mail Extension) X.509 DES Triple-DES RC2,
Pretty Good Privacy (PGP) PGP Phil Zimmermann 1991 PGP IDEA RSA SHA-1 MD5... ZIP http://www.pgpi.org/
SET (Secure Electronic Transaction) 1995 VISA Mastercard SET SET DES RSA SHA-1 (Dual Signature)
SET ( ) VisaNet
(Authentication) (Confidentiality) (Integrity) (Non-repudiation)