To get a Cisco IOU license on the GNS3 VM. ('Cisco IOU License Generator - Kal 2011, python port of 2006 C version') import os import socket import hashlib import struct # get the host id and host name to calculate the hostkey hostid=os.popen('hostid').read.strip hostname = socket.gethostname ioukey=int(hostid,16) for.
Cisco IOU License Generator. Originally found at I have done a few changes to it. Make the file executable with ' chmod +x CiscoKeyGen.py ' and execute it './CiscoKeyGen.py '.

Introduction
Recommendations for Cryptographic Algorithms
Introduction to Cryptography
Next Generation Encryption
NGE Background Information
Categories of Cryptographic Algorithms
Symmetric Key
Public Key
Elliptic Curve
Hash
Security Levels
Cryptographic Algorithm Configuration Guidelines
IPsec VPN with Encapsulating Security Payload
Internet Key Exchange in VPN Technologies
Transport Layer Security and Cipher Suites
Acknowledgments
References
Appendix A: Minimum Cryptography Recommendations

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Over the years, numerous cryptographic algorithms have been developed and used in many different protocols and functions. Cryptography is by no means static. Steady advances in computing and the science of cryptanalysis have made it necessary to adopt newer, stronger algorithms and larger key sizes. Older algorithms are supported in current products to ensure backward compatibility and interoperability. However, some older algorithms and key sizes no longer provide adequate protection from modern threats and should be replaced. This paper summarizes the security of cryptographic algorithms and parameters, gives concrete recommendations regarding which cryptography should be used and which cryptography should be replaced, and describes alternatives and mitigations.

The following table can help customers migrate from legacy ciphers to current or more secure ciphers. The table explains each cryptographic algorithm that is available, the operations that each algorithm supports, and whether an algorithm is Cisco's best recommendation. Customers should pay particular attention to algorithms designated as Avoid or Legacy. The status labels are explained following the table.

Table 1. Recommendations for Cryptographic Algorithms

Algorithm	Operation	Status	Alternative	QCR¹	Mitigation
DES	Encryption	Avoid	AES	—	—
3DES	Encryption	Legacy	AES	—	Short key lifetime
RC4	Encryption	Avoid	AES	—	—
AES-CBC mode AES-GCM mode	Encryption Authenticated encryption	Acceptable NGE²	AES-GCM —	✓ (256-bit) ✓ (256-bit)	— —
DH-768, -1024 RSA-768, -1024 DSA-768, -1024	Key exchange Encryption Authentication	Avoid	DH-3072 (Group 15) RSA-3072 DSA-3072	— — —	— — —
DH-2048 RSA-2048 DSA-2048	Key exchange Encryption Authentication	Acceptable	ECDH-256 — ECDSA-256	— — —	— — —
DH-3072 RSA-3072 DSA-3072	Key exchange Encryption Authentication	Acceptable	ECDH-256 — ECDSA-256	— — —	— — —
MD5	Integrity	Avoid	SHA-256	—	—
SHA-1	Integrity	Legacy	SHA-256	—	—
SHA-256 SHA-384 SHA-512	Integrity	NGE	SHA-384 — —	— ✓ ✓	— — —
HMAC-MD5	Integrity	Legacy	HMAC-SHA-256	—	Short key lifetime
HMAC-SHA-1	Integrity	Acceptable	HMAC-SHA-256	—	—
HMAC-SHA-256	Integrity	NGE	—	✓	—
ECDH-256 ECDSA-256	Key exchange Authentication	Acceptable	ECDH-384 ECDSA-384	— —	— —
ECDH-384 ECDSA-384	Key exchange Authentication	NGE	— —	— —	— —
1. QCR = quantum computer resistant. 2. NGE = next generation encryption.

Avoid: Algorithms that are marked as Avoid do not provide adequate security against modern threats and should not be used to protect sensitive information. It is recommended that these algorithms be replaced with stronger algorithms.

Legacy: Legacy algorithms provide a marginal but acceptable security level. They should be used only when no better alternatives are available, such as when interoperating with legacy equipment. It is recommended that these legacy algorithms be phased out and replaced with stronger algorithms.

Acceptable: Acceptable algorithms provide adequate security.

Next generation encryption (NGE): NGE algorithms are expected to meet the security and scalability requirements of the next two decades. For more information, see Next Generation Encryption.

Quantum computer resistant (QCR): In recent years, there has been attention on quantum computers (QCs) and their potential impact on current cryptography standards. Although practical QCs would pose a threat to crypto standards for public-key infrastructure (PKI) key exchange and encryption, no one has demonstrated a practical quantum computer yet. It is an area of active research and growing interest. Although it is possible, it can't be said with certainty whether practical QCs will be built in the future. An algorithm that would be secure even after a QC is built is said to have postquantum security or be quantum computer resistant (QCR). AES-256, SHA-384, and SHA-512 are believed to have postquantum security. There are public key algorithms that are believed to have postquantum security too, but there are no standards for their use in Internet protocols yet.

Cisco is committed to providing the best cryptographic standards to our customers. NGE still includes the best standards that one can implement today to meet the security and scalability requirements for network security in the years to come or to interoperate with the cryptography that will be deployed in that time frame. The biggest threat to crypto nowadays is another high-impact implementation issue, not a QC. So while we need to get smart about postquantum crypto, we need to do it in a way that doesn't create more complexity and less robustness. Cisco will remain actively involved in quantum resistant cryptography and will provide updates as postquantum secure algorithms are standardized.

Short key lifetime: Use of a short key lifetime improves the security of legacy ciphers that are used on high-speed connections. In IPsec, a 24-hour lifetime is typical. A 30-minute lifetime improves the security of legacy algorithms and is recommended.

Cryptography can provide confidentiality, integrity, authentication, and nonrepudiation for communications in public networks, storage, and more. Some real-world applications include protocols and technologies such as VPN networks, HTTPS web transactions, and management through SSH.

Over the years, some cryptographic algorithms have been deprecated, 'broken,' attacked, or proven to be insecure. There have been research publications that compromise or affect the perceived security of almost all algorithms by using reduced step attacks or others such as known plaintext, bit flip, and more. Additionally, advances in computing reduce the cost of information processing and data storage to retain effective security. Because of Moore's law and a similar empiri

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