Search notes:
Public Key Cryptography
Any
cryptographic system that uses the public key and private key pair is said to be
public key cryptography or
asymmetric cryptography.
The best-known uses for public key cryptography are:
- authentication (Profing that holder of private key sent a message)
- encryption (Only the holder of the private key can decrypt a message encrypted with a public key.
Asymmetric encryption is slower than symmetric encryption.
RSA is one of the dominant public key cryptosystems.
Apparently, a public/private key pair can be generated with ssh-keygen
.
Public Key Cryptographic Standards (PKCS)
The PKCS are a set of standards which are published by RSA Security LLC.
PKCS #1 | RSA Cryptography Standard | RFC 8017 |
PKCS #3 | Diffie–Hellman Key Agreement Standard | |
PKCS #5 | Password-based Encryption Standard | RFC 8018, PBKDF2 |
PKCS #6 | Extended-Certificate Syntax Standard | |
PKCS #7 | Cryptographic Message Syntax Standard | RFC 2315 |
PKCS #8 | Private-Key Information Syntax Standard | Storing private key information, see RFC 5958 and Public key cryptography |
PKCS #9 | Selected Attribute Types | RFC 2985 |
PKCS #10 | Certification Request Standard | RFC 2986 |
PKCS #11 | Cryptographic Token Interface | |
PKCS #12 | Personal Information Exchange Syntax Standard | RFC 7292 |
PKCS #15 | Cryptographic Token Information Format Standard | |
Some standards (which are not listed in the table above) are withdrawn or were not published.
Possible notation
A
is
Alice's public key, and
a
is her private key. Thus,
{msg}A
is an encrypted cyphertext,
{msg}a
is a signed message.
Surreptious forwarding
Alice sends Bob a signed and encrypted message {{msg}a}B
.
Using his private key, Bob gets {msg}a
.
Using Charlies public key, Bob encrypts this to {{msg}a}C
and sends it to Charlie.
Using his private key, Charlie decrypts it to {msg}a
and then uses Alice's public key to (naively) verify that Alice sent {msg}
.
Thus, Charlie is under the wrong impression that Alice sent {msg}
to Charlie rather than to Bob.