NIST Algorithm Comparisons and Key Size Recommendations

Equivalent Algorithm Strengths

 

Bits of Security
Cipher
Example
ECC
D-H / DSA / RSA
80
2TDEA
160-223 (163)
1024 / 160
112
3TDEA
224-255 (233)
2048 / 224
128
AES-128
256-383 (283)
3072 / 256
192
AES-192
384-511 (409)
7680 / 384
256
AES-256
512+ (571)
15360 / 512

The table on this page is taken from NIST SP-800-57 (May 2006), and is in fairly good agreement with RFC 4492, " ECC Cipher Suites for TLS," Blake-Wilson et al., May 2006 (numbers in italics). The latter document is based on:

Lenstra, A. and E. Verheul, "Selecting Cryptographic Key Sizes," Journal of Cryptology 14 (2001) 255-293