I have read papers ,  that have presented techniques on extracting symmetric encryption keys from memory during the process of encryption. There are tools  that can extract AES keys from memory.
These techniques look for round keys in the memory using a sliding window approach. However, I have only seen them implemented for
AES keys. Does that mean that for other symmetric ciphers, such as
RC4, we cannot feasibly locate the encryption keys in memory during encryption using similar techniques? Do other symmetric encryption algorithms have such patterns that can help locate keys in memory?
 Halderman, J. A., Schoen, S. D., Heninger, N., Clarkson, W., Paul, W., Calandrino, J. A., ... & Felten, E. W. (2009). Lest we remember: cold-boot attacks on encryption keys. Communications of the ACM, 52(5), 91-98.
 Kaplan, B. (2007). RAM is Key Extracting Disk Encryption Keys From Volatile Memory.