Hi All,

I'm trying to get user's profile by GUID. I'm following OAuth Authorization Flow (http://developer.yahoo.com/oauth/guide/oauth-auth-flow.html) and everything is fine except the last step (http://developer.yahoo.com/oauth/guide/oauth-make-request.html). I tried a lot of ways to generate signature base string and actual signature, but every time I got this HTTP header:
    WWW-Authenticate: OAuth oauth_problem="signature_invalid", realm="yahooapis.com"

I'm using ASP.NET web-application (C#) to make requests to Yahoo. I call the following URL:
    http://social.yahooapis.com/v1/user/<GUID>/profile?format=json  
where <GUID> is user's GUID from https://api.login.yahoo.com/oauth/v2/get_token request

I call that URL with Authorization HTTP header as described in OAuth Make Request documentation. I use Token Secret from get_token request.
My Authorization HTTP header has data similar to this:
OAuth realm="yahooapis.com", oauth_consumer_key="<ConsumerKey>", oauth_token="A%3dyTkQq23w5wxSqyJj8WAFQK7cEahL5oADb2ktY0zuvd8uL3ZG0l3IOBkUohfDXxk_Psa71nNbAQY6ksnK6AWs1mPkd_Q53blZ6EMVQenwb3wRy.QHD6k3wgnMHq6SVByGjAiST3oN2bsOFubJG1tHmjNUiS3x7LQb5UeHRMusBSKhw5zlj.JiRyU3ky1bNxeQIGKzHtuWr3A14giy9xhBygjtPLPcraWRHN_4foxc4XTj2eG7MGuhcEuHFn.P83ocXaqkA5Sn.9R7W1NN4jAG2B.58QG4GQ_j6K0NftH7Lq3vpddgzSJndX2PgcwiDlG3XJb.M9j39lRkjeKkuNfesb06OqYF_LHIQWVf3Y8eZ8QlrIny6Ff5Dr4fkd4kBcXVkjGL2M9m6YFufKghf7ftMoMe7hzhVTQ_J__EhQaNcI8ijtCblo3QAzdAGiG0lX.x75Ts00Ht_dbPKzO708IYD0HH97ZvS4JiV73CZc5ax3iecUuo_16MkzvjWFgCIQ9XoTU9YMdLF2dqnvVD8vqJ._3LrizuHoGfwtYxUy61b6luWgdqn5Rs6g7y058HQuTkX8469uKVtraB52opVXAUbv439m6RLsoEQhqcKXdBpvvRXVnDTe6Ihb_QQs304QxFOUwLXu29qm4nHLY.30O2IQOqObvbgBesChWCTj4D4f2kQ2S13RinawW.Ziw8AVPw0xH_LrWzTqoCXdYOR6lo4nJ4vduv0Do4GkhsUk_pooZhjPZCQrUViHw85I1vtbM0Td4tt5BiMCdfQO6QDZ4gKyafzut00GAvOxwFsIgeweJJ8K8p.eENeWwa93.niKImEKe6FK4M6LRPnukd.rKE.BO_6n.BGSPb1kB_og--", oauth_signature_method="HMAC-SHA1", oauth_signature="kQc8rqXtm9J5OKo5WSbjM5H24vM%3d", oauth_timestamp="1342702968", oauth_nonce="Sumo.OAuth2.YahooProvider_63bba3c7-a675-4284-bd0d-9f13f103122e", oauth_version="1.0"

When I'm generating signature I have key and signature base string similar to the following:
Key:
<ConsumerSecret>&cee5c082b5c2a452a3d4ee195a18d9888a0478d6
Signature Base String:
GET&http%3a%2f%2fsocial.yahooapis.com%2fv1%2fuser%2f<GUID>%2fprofile&format%3djson%26oauth_consumer_key%3d<ConsumerKey>%26oauth_nonce%3dSumo.OAuth2.YahooProvider_63bba3c7-a675-4284-bd0d-9f13f103122e%26oauth_signature_method%3dHMAC-SHA1%26oauth_timestamp%3d1342702968%26oauth_token%3dA%3dyTkQq23w5wxSqyJj8WAFQK7cEahL5oADb2ktY0zuvd8uL3ZG0l3IOBkUohfDXxk_Psa71nNbAQY6ksnK6AWs1mPkd_Q53blZ6EMVQenwb3wRy.QHD6k3wgnMHq6SVByGjAiST3oN2bsOFubJG1tHmjNUiS3x7LQb5UeHRMusBSKhw5zlj.JiRyU3ky1bNxeQIGKzHtuWr3A14giy9xhBygjtPLPcraWRHN_4foxc4XTj2eG7MGuhcEuHFn.P83ocXaqkA5Sn.9R7W1NN4jAG2B.58QG4GQ_j6K0NftH7Lq3vpddgzSJndX2PgcwiDlG3XJb.M9j39lRkjeKkuNfesb06OqYF_LHIQWVf3Y8eZ8QlrIny6Ff5Dr4fkd4kBcXVkjGL2M9m6YFufKghf7ftMoMe7hzhVTQ_J__EhQaNcI8ijtCblo3QAzdAGiG0lX.x75Ts00Ht_dbPKzO708IYD0HH97ZvS4JiV73CZc5ax3iecUuo_16MkzvjWFgCIQ9XoTU9YMdLF2dqnvVD8vqJ._3LrizuHoGfwtYxUy61b6luWgdqn5Rs6g7y058HQuTkX8469uKVtraB52opVXAUbv439m6RLsoEQhqcKXdBpvvRXVnDTe6Ihb_QQs304QxFOUwLXu29qm4nHLY.30O2IQOqObvbgBesChWCTj4D4f2kQ2S13RinawW.Ziw8AVPw0xH_LrWzTqoCXdYOR6lo4nJ4vduv0Do4GkhsUk_pooZhjPZCQrUViHw85I1vtbM0Td4tt5BiMCdfQO6QDZ4gKyafzut00GAvOxwFsIgeweJJ8K8p.eENeWwa93.niKImEKe6FK4M6LRPnukd.rKE.BO_6n.BGSPb1kB_og--%26oauth_version%3d1.0

I'm looking for any help here.

Thanks in advance,
Maxim.