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Cryptography converts data into a particular form so that only those for whom it is intended can read and process it. The converted data is however unreadable for an unauthorized user
- A symmetric key algorithm requires the same key for both encryption of a plaintext and decryption of a cipher text.
- This same key is also called a shared secret.
- Symmetric key algorithms are generally much faster to encrypt and decrypt a message than asymmetric key algorithms.
- AES (Advanced Encryption Standard), Triple DES (Data Encryption Standard) uses this algorithm
- An asymmetric key algorithm requires two keys called a public and a private key. One of the key is used for encryption of a plaintext and the other key is used for decryption of the cipher text
- A big disadvantage is that asymmetric key algorithms are generally much slower to encrypt and decrypt a message than symmetric key algorithms
- The advantage of using an asymmetric key algorithm is that any sender can encrypt a message using the receiver public key, but only the receiver can decrypt the cipher text using its private key
- A public key and private key are mathematically interconnected. Meaning each public key has only one corresponding private key.
- RSA (Rivest Shamir Adleman), ECDSA (Elliptic Curve Digital Signature Algorithm) uses this algorithm
- In Blockchain the Elliptic Curve Digital Signature Algorithm is often used.
- A hash function converts data of any size into a string of a fixed size
- A small change in the data will result in a complete different hash
- When to different inputs produces the same hash, it is called a hash collision
- A hash function is considered “collision resistant” when it is very hard to find two inputs that hash to the same output
- There are many different hash functions. Here are just a few:
| Hash function | Hash length | Secure |
|---|---|---|
| md5 | 128 bits (32 symbols) | No |
| ripemd160 | 160 bits (40 symbols) | Yes |
| sha1 | 160 bits (40 symbols) | No |
| sha256 | 256 bits (64 symbols) | Yes |
| keccak-256 | 256 bits (64 symbols) | Yes |
md = message digest
ripemd = RACE integrity primitives evaluation message digest
sha = secure hash algorithm
- A digital signature is equivalent of a handwritten signature but it is much more secure, a handwritten signature can be faked
- A digital signature provides the recipient the following information:
- the message was created by a known sender (authentication),
- the sender cannot deny having sent the message (non-repudiation),
- the message was not altered in transit (integrity)
Resources credit: Mobile Fish