Scapysec

I am the author of a little project called Scapysec. Scapysec is an extension to scapy (a Packet generator written in Python) and scapy6 (IPv6 for Scapy) to handle IPsec packets with both protocols. Thus Scapysec may encrypt/decrypt ESP Packets, compute the authentication, send or receive invalid/valid ESP packets. Currently Scapysec supports:

• Encryption Algorithms:
  • NULL Encryption Algorithm.
  • TripleDES-CBC [RFC2451] : keylen 192 bits.
  • AES-CBC[RFC3602] : keylen 128 and 192/256 bits.
  • AES-CTR [RFC3686] : keylen 160/224/288 bits. (32 bits for Nonce).
  • DES-CBC [RFC2405] : keylen 64 bits.
  • BLOWFISH-CBC : Any keylen.
  • CAST5-CBC[Draft] : keylen 40, 48, 56, ..., 120, and 128 bits.
• Authentication Algorithms:
  • NULL Authentication
  • HMAC-SHA1-96 [RFC2404] : Any keylen
  • HMAC-SHA256-96 [Draft] : Any keylen
  • HMAC-MD5-96 [RFC2403] : Any keylen
  • HMAC-RIPEMD160-96 [RFC2857] : Any keylen
  • AES-XCBC-MAC-96 [RFC3566] : keylen 128 bits

This is an old Personal Free Project (thus for an old version ;-( of Scapy) that you can download Here.
For more information on how to use it, have a look Here.
If you need XCBC-MAC or XCBC-PRF you may get my implementations Here.