Knowledge Base
Diffie-Hellman Parameter
D

1024-bit ProFTPD 1.2.8 builtin DH parameter

Summary

Name:
1024-bit ProFTPD 1.2.8 builtin DH parameter
Key size:
1024 bits
Publishers:

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Security

D
Key Size
Name

1024

Security

The Diffie-Hellman ephemeral public key parameter[409][410][411] with prime size less or equal than 1024-bit[424] is weakened against logjam attack[7][8][9][10], but can only be exploited by a national states.

Recommendations

Use a well-known Diffie-Hellman ephemeral public key parameter[426][427][428], or generate a custom Diffie-Hellman ephemeral public key parameter[409][410][411] with a size greater or equal than 2048 bits but less or equal than 4096 bits. In the case of custom parameters, validate that the prime is a safe prime[176] to avoid a small subgroup confinement attack[72][73].

A+
Prime
Name

Safe Prime

Security

Diffie-Hellman ephemeral public key parameter[409][410][411] contains a safe prime[176], so the connection is certainly not vulnerable to a small subgroup confinement attack[72][73].

A
Post-Quantum
Name

False

Security

The Diffie-Hellman[99][100][101][102][103] key exchange provides no protection against a cryptanalytic attack by a quantum computer, and no classical Diffie-Hellman does — just as no classical elliptic curve does — because a quantum computer breaks the hardness assumption they rely on. Only a hybrid key exchange (a classical algorithm combined with a post-quantum cryptography[158][159] one) or a pure post-quantum algorithm is quantum-safe.

Recommendations

Enable a hybrid key exchange or a pure post-quantum algorithm on your server, and prefer it where the configuration allows, so the connection stays secure against a future quantum computer.

Parameter Numbers

Prime (p)
0xc1d89c90b1587ce15670d7616c00e6e799049f86d9b411092318aa19ca497ca89df7433aafc31f0eaebbf2ea5b62a15f7c26a8b45d2a25ab88702706d0f501d96a1f482d9cecfea845971dc08affe5e179df8531fc589135e8c7da557baaddc20a9434f7b44a913b1e16892a04475de942475e3061e842c123c7977863369d3b
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Generator (g)
0x2
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Representations

PEM

Default private value length
-----BEGIN DH PARAMETERS-----
MIGHAoGBAMHYnJCxWHzhVnDXYWwA5ueZBJ+G2bQRCSMYqhnKSXyonfdDOq/DHw6u
u/LqW2KhX3wmqLRdKiWriHAnBtD1AdlqH0gtnOz+qEWXHcCK/+Xhed+FMfxYkTXo
x9pVe6rdwgqUNPe0SpE7HhaJKgRHXelCR14wYehCwSPHl3hjNp07AgEC
-----END DH PARAMETERS-----
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Small private value length
-----BEGIN DH PARAMETERS-----
MIGLAoGBAMHYnJCxWHzhVnDXYWwA5ueZBJ+G2bQRCSMYqhnKSXyonfdDOq/DHw6u
u/LqW2KhX3wmqLRdKiWriHAnBtD1AdlqH0gtnOz+qEWXHcCK/+Xhed+FMfxYkTXo
x9pVe6rdwgqUNPe0SpE7HhaJKgRHXelCR14wYehCwSPHl3hjNp07AgECAgIA4Q==
-----END DH PARAMETERS-----
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PARI/GP

powermod(x, k, m) = lift(Mod(x, m) ^ k);

g = 0x2;
p = 0xc1d89c90b1587ce15670d7616c00e6e799049f86d9b411092318aa19ca497ca89df7433aafc31f0eaebbf2ea5b62a15f7c26a8b45d2a25ab88702706d0f501d96a1f482d9cecfea845971dc08affe5e179df8531fc589135e8c7da557baaddc20a9434f7b44a913b1e16892a04475de942475e3061e842c123c7977863369d3b;
s = 256;

a = 2 ^ (s - 1) + random(2 ^ (s - 1));
A = powermod(g, a, p);

b = 2 ^ (s - 1) + random(2 ^ (s - 1));
B = powermod(g, b, p);

S = powermod(B, a, p);
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LaTeX

$\begin{eqnarray}
p \equiv 0xc1d89c90b1587ce15670d7616c00e6e799049f86d9b411092318aa19ca497ca89df7433aafc31f0eaebbf2ea5b62a15f7c26a8b45d2a25ab88702706d0f501d96a1f482d9cecfea845971dc08affe5e179df8531fc589135e8c7da557baaddc20a9434f7b44a913b1e16892a04475de942475e3061e842c123c7977863369d3b \\
g \equiv 0x2 \\
\\
a \in \mathbb{Z}_q \\
b \in \mathbb{Z}_q \\
\\
A \equiv g^a \pmod{p} \\
B \equiv g^b \pmod{p} \\
\\
S \equiv {(g^{a})}^{b}={(g^{b})}^{a}=g^{ab} \pmod{p}
\end{eqnarray}$
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