Cryptography
•
Secret
-
Key and Public
-
Key Cryptography
•
Cryptographic Primitives
•
Common Public
-
Key Cryptosystems
•
Comparison of Security Levels of PKCS
•
Emerging Trends
•
IEEE P1363
Private
-
Key Cryptography
Secret Message
Private Key
Private Key
Secret Message
Data Encryption
Sender
Receiver
Public
-
Key Cryptography
Secret Message
Recipient’s
Public Key
Secret Message
Recipient’s
Private Key
Interloper’s
Private Key
Cannot decrypt, because
message opens only with
the recipient’s Private key
Data Encryption
Public
-
Key Cryptography
Random Message
Private Key
Garbled Message
Public Key
Signature Verified
Yes / No
Digital Signature
Authentication
B
Party B
Party A
Party A
Party B
Random Message
{random message} B’s Private Key
Random Message
,Yeah! This is B!
{
Random Message
, Yeah! This is B! } B’s Private Key
Random Message
Cryptographic Systems
•
Integer Factorization Systems
p * q = n
•
Discrete Logarithm Systems
y = g
x
( mod p )
•
Elliptic Curve Cryptosystems
Y
2
= x
3
+ ax + b (mod p)
Comparison of Security Levels
•
Current acceptable
security level is
10
12
MIPS
Comparison of security levels ECC and RSA & DSA
0
1000
2000
3000
4000
5000
6000
10000
1000000000
1E+12
1E+20
1E+36
Time to break key (MIPS years)
Key size (bits)
ECC
RSA & DSA
Emerging Trends
•
Secure Channels
-
Secure Socket Layer
(SSL), Private Communications
Technology (PCT)
•
Server Gated Cryptography (SGC)
•
Authenticode
•
CryptoAPI
Secure Socket Layer
Client
Server
Hello
C
Hello
S
Certificate
S
(Client verifies Certificate
S
)
(Client extracts P
S
from Certificate
S
)
(Client selects algorithm A)
(Client generates session key K)
{K} P
S
SpecifyAlgorithm (A)
{Finished
C
} K
SpecifyAlgorithm (A)
{Finished
S
} K
{DATA
C
} K
{DATA
S
} K
CryptoAPI Model
Application
Certificate
Functions
Simplified
Crypto Functions
Base Cryptographic Functions
Microsoft
Base Provider
Smart Card
Cryptographic Service Providers
Crypto API Interface
IEEE P1363
•
Comprehensive
coverage of the
primitive and schemes
of the three families of
PKCS
•
Goal is to provide
guidance but leave
flexibility
•
No key lengths
•
Discusses Key
Agreement, Digital
Signatures and
Encoding Schemes
•
A forum for
discussion
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