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is Is a collision attack possible on md5MD5 if message is known partially

Is it possible to find m'$m'$ such that md5(m'+m1)=md5(m1+m2)$\operatorname{MD5}(m'||m_1)=\operatorname{MD5}(m_1||m_2)$ if iI know m2$m_2$ and md5(m1+m2) $\operatorname{MD5}(m_1||m_2)$? is Is this a collision or pre-imagea preimage attack.
Also?

Also in this case is it possible to find m'$m'$ and H$H$ such that md5(m1+m')=H$\operatorname{MD5}(m_1||m')=H$ if iI know md5(m1+m2)$\operatorname{MD5}(m_1||m_2)$ and m2 $m_2$? Basically

Basically a message is like : (M,md5(M|m1))$(M,\operatorname{MD5}(M||m1))$ is sent from server to client ( onlyonly client and and server know m1 $m_1$).So can I being the middle man So is there an attack in this scenario  ?

is collision attack possible on md5 if message is known partially

Is it possible to find m' such that md5(m'+m1)=md5(m1+m2) if i know m2 and md5(m1+m2) ? is this a collision or pre-image attack.
Also in this case is it possible to find m' and H such that md5(m1+m')=H if i know md5(m1+m2) and m2 ? Basically a message is like : (M,md5(M|m1)) sent from server to client ( only client and server know m1 ).So can I being the middle man attack in this scenario  ?

Is a collision attack possible on MD5 if message is known partially

Is it possible to find $m'$ such that $\operatorname{MD5}(m'||m_1)=\operatorname{MD5}(m_1||m_2)$ if I know $m_2$ and $\operatorname{MD5}(m_1||m_2)$? Is this a collision or a preimage attack?

Also in this case is it possible to find $m'$ and $H$ such that $\operatorname{MD5}(m_1||m')=H$ if I know $\operatorname{MD5}(m_1||m_2)$ and $m_2$?

Basically a message like $(M,\operatorname{MD5}(M||m1))$ is sent from server to client (only client and server know $m_1$). So is there an attack in this scenario?

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is collision attack possible on md5 if message is known partially

Is it possible to find m' such that md5(m'+m1)=md5(m1+m2) if i know m2 and md5(m1+m2) ? is this a collision or pre-image attack.
Also in this case is it possible to find m' and H such that md5(m1+m')=H if i know md5(m1+m2) and m2 ? Basically a message is like : (M,md5(M|m1)) sent from server to client ( only client and server know m1 ).So can I being the middle man attack in this scenario ?