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Questions tagged [x25519]

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10
votes
1answer
149 views

How does the process of creating a new secure Elliptic Curve look like?

I'm especially curious about the technique djb would have used to come up with his Curve 25519. Say I have already written down my goals, such as - Twist Secure, Speed, Side Channel resistance, etc. ...
2
votes
2answers
65 views

Curve25519 Key Exchange Bit Security

Please note I am new to Cryptography in general. Sorry if I do not use the correct terminology/my question has some fundamental flaw. Alice and Bob want to communicate securely over an insecure ...
6
votes
2answers
232 views

Curve 25519 (X25519, Ed25519) Convert coordinates between Montgomery curve and twisted Edwards curve

I have some misunderstanding about EdDSA conversion coordinates between Montgomery curve and twisted Edwards curve. In https://tools.ietf.org/html/rfc7748 I see that a base point for Curve25519 is ...
2
votes
1answer
203 views

X25519 - why openssl shows 253 bits?

When using ECDHE with Curve25519 with openssl: Server Temp Key: X25519, 253 bits I thought when we use X25519, it use 256 bit key. Why openssl shows the server temp key as 253 bits?
20
votes
1answer
1k views

Distinguishing x25519 public keys from random?

I recently read a piece of protocol that avoided sending ephemeral x25519 keys in the clear as an effort to foil deep-packet inspection. I understand that x25519 public keys are effectively 255 bits, ...